Reach Us
Niir Project Consultancy Services (NPCS)
AN ISO 9001 : 2015 CERTIFIED COMPANY
106-E, Kamla Nagar,Opposite Spark Mall,
New Delhi-110007, India.
Email: npcs.ei@gmail.com,
info@entrepreneurindia.co
Tel: 91-11-23843955, 23845654, 23845886, +91-8800733955
Mobile: +91-9811043595
Fax: 91-11-23845886
Web: www.entrepreneurindia.co
  • Join Us On
Reach Us
Quick Enquiry
 
   
   
Quick Enquiry
 
 
The Complete Book on Adhesives, Glues & Resins Technology (with Process & Formulations) 2nd Revised Edition ( ) ( Best Seller ) ( ) ( ) ( )
Author NPCS Board of Consultants & Engineers ISBN 9788178331614
Code ENI185 Format Paperback
Price: Rs 1675   1675 US$ 150   150
Pages: 616 Published 2016
Publisher Select
Usually Ships within 5

An adhesive is a material used for holding two surfaces together. In the service condition that way adhesives can be called as “Social” as they unite individual parts creating a whole. A useful way to classify adhesives is by the way they react chemically after they have been applied to the surfaces to be joined. There is a huge range of adhesives, and one appropriate for the materials being joined must be chosen. Gums and resins are polymeric compounds and manufactured by synthetic routes. Gums and resins largely used in water or other solvent soluble form for providing special properties to some formulations. More than 95% of total adhesive used worldwide are based on synthetic resins. Gums and resins have wide industrial applications. They are used in manufacture of lacquers, printing inks, varnishes, paints, textiles, cosmetics, food and other industries.

 

Increase in disposable income levels, rising GDP and booming retail markets are propelling growth in packaging and flexible packaging industry. Growth of disposable products is expected to increase, which leads to increase in consumption of adhesives in packaging industry. The global value of adhesive resins market is estimated to be $11,339.66 million and is projected to grow at a CAGR of about 4.88% in coming years. Rapid urbanization coupled with growing infrastructure and real estate construction projects is projected to further fuel demand for adhesives in India.

 

This handbook covers photographs of plant & machinery with supplier’s contact details and manufacturing aspects of various adhesives, glues & resins. The major contents of the book are glues of animal origin, fish glues, animal glues, casein glues & adhesives, blood albumen glues, amino resin adhesives, cyanoacrylate adhesives, epoxy resin adhesives, phenolic resin adhesives, polychloroprene resin adhesives, polysulfide sealants & adhesives, resorcinolic adhesives, furan resin adhesives, lignin adhesives, polyamide adhesives, rosin adhesive, tannin adhesives, terpene based adhesives, starch adhesives, acrylic adhesives and sealants, pressure sensitive adhesives, hot melt adhesives, alkyd resins, acrylic modified alkyd resins, alkyd –amino combinations based on neem oil, amino resins, carbohydrate modified phenol- formaldehyde resins, epoxy resins etc.

 

It will be a standard reference book for professionals, entrepreneurs, those studying and researching in this important area and others interested in the field of adhesives, glues & resins technology.

 

 

 

Adhesives

  1.  Glues of Animal Origin                                               

       Properties

       Methods of Manufacture

       Commercial Grades and Specifications

       Methods of Analysis

       Sampling

       Procedure

       Identification

       Physical Measurements

       Determination of Other Constituents

  2.  Fish Glues                                                                      

       Introduction

       Manufacturing Process

       Properties

       Applications & Formulations

       Rubber-to-Steel

       Strawboard-to-Steel

       Rubber-or Cork-to-Plywood

       Paper-to-Steel

       Straight Line Gluing

  3.  Animal Glues                                                                

       Introduction

       Chemical Composition

       Manufacture of Animal Glues

       Properties

       Liquid Animal Glues

       Formulation & Applications

       Methods of Application

 4.   Casein Glues and Adhesives                                        

       Introduction

       Properties

       Casein Blend Glues

       Lime free Casein Adhesives

       Applications

       Casein Adhesives for Bonding Paper

       Casein Adhesive for Binding Dissimilar Materials

  5.  Blood Albumen Glues                                                  

       Introduction

       Solubility Categories

       Properties

       Blood-Soybean Flour Combinations

       Mold Resistance

       Application

  6.  Amino Resin Adhesives                                               

       Introduction

       Manufacturing Technology

       Urea Adhesive for Plywood

       Urea Adhesive for Particle Board

       Spray Dried Melamine-formaldehyde Resins

       Foundry Resin

       Aniline-Formaldehyde Resin

       Ø Represents benzene ring

       Sulfonamide-Formaldehyde Resins

       Applications

       Adhesives for Hardwood Plywood

       Sand Core Binder

       Water Proof Corrugated Board

       Compounding and Formulation

  7.  Cyanoacrylate Adhesives                                             

       Introduction

       Bonding with Cyanoacrylates

       Adhesive Properties

       Applications

  8.  Epoxy Resin Adhesives                                                

       Introduction

       Chemistry

       Epoxy Novolac Resins

       Flexible Epoxy Resins

       Epoxidized Olefins

       Speciality Epoxy Resins & Derivatives

       Epoxy Esters of Rosin

       Epoxy Esters of Styrenated Rosin

       Epoxy Esters of Disproportionated Rosin

       Epoxy Novolac Esters

       Epoxy Ester of Maleopimaric Acid

       Compounding

       Curing Agents

       Diluents

       Modifiers

       Flexibilizers

       Fillers

       Accelerators

       Speciality Additives

       Manufacture of Adhesives

  9.  Phenolic Resin Adhesives                                           

       Introduction

       Resole resin

       Novalac Resins

       Manufacture

       Applications and Formulations

       Contact Adhesives

       Adhesive Compounding

       Nitrile/Phenolic Contact Adhesives

       Structural Adhesives

       Vinyl/Phenolic

       Epoxy/Phenolic

       Hot Melt Adhesives

       Hot Melt Vinyl Film to Wood Laminating Adhesives

       Pressure Sensitive Adhesives (PSA)

10.  Polychloroprene Resin Adhesives                              

       Introduction

       Types of Polychloroprene

       Applications and Formulations

       Applications

 

11.  Polyester Resin Adhesives                                          

       Introduction

       Linear Polycarbonates

       Polymerized Oils

       Alkyd Resins

       Unsaturated Polyester Adhesives

       Adhesives for Flexible Printed Circuit

       Allyl Ester Adhesives

12.  Polyethyleneimine in Adhesives                                

       Introduction

       Applications

       General Adhesives

       Tie Coat Adhesives

13.  Polysulfide Sealants and Adhesives                          

       Introduction

       Polysulfide Sealants

       Chemistry

       Compounding

       Curing Agent

       Retarder

       Reinforcement

       Adhesion Additives

       Primers

       Improved Heat Resistance

       Applications

       Adhesives from Polysulfide Liquid Polymer
       Epoxy Resin Reactions

14.  Resorcinolic Adhesives                                                

       Introduction

       Resorcinol-Phenol Formaldehyde Resins

       Modified Resorcinol Resins

       Aspects of Adhesion Mechanism

       Formulation of Glue Mixtures

       Laminating

15. Ethylene Copolymer Hot Melt Adhesives

       Introduction

       Crystallinity

       Compatibility

       Pressure Sensitive Tack

       Hot Melt Adhesive Formulating

       Book Binding Adhesives

       Carton and Case Sealing Adhesives

       Carpet Application

       Shoe Adhesives

       Pressure Sensitive Adhesives (PSA)

       Furniture Adhesives

16.  Furan Resin Adhesives                                                

       Introduction

17.  Isocyanate Adhesives                                                   

       Introduction

       Advantages of Isocyanate Adhesives

       Disadvantages of Isocyanates

       Applications

       Types and uses of Isocyanate based Adhesive System

18.  Lignin Adhesives                                                          

       Introduction

       Formulations

19.  Polyamide Adhesives                                                   

       Introduction

      Class I: Thermoset Adhesives Containing Liquid                                                                                    

            Polyamide Curing Adhesives

       Class II: Nylon-Epoxy Resins

       Class III: Thermoplastic Hot Melt Polyamide Adhesives

       Class IV: Thermoplastic-Thermoset Adhesives

20.  Polyimide Adhesives                                                    

       Introduction

       Adhesive and Bonding Technology

       Foam System

21.                                                              Rosin Adhesives           

       Introduction

       Applications

       Formulations

       Solvent Adhesives

       Emulsion Adhesives

       Hot Melt Adhesives

       Methods of manufacture

22.  Silicone Adhesives and Sealants                                

       Introduction

       Chemistry

       Oxime silane

       Properties

       Rheological Characteristics

       Thermal Stability

       Weathering Characteristics

       Adhesion Characteristics

       Applications

       Industrial

       Construction

23.  Tannin Adhesives                                                         

       Introduction

       Formulation

24.  Terpene Based Adhesives                                           

       Introduction

       Chemistry

       Beta-pinene resins

       Dipentene resins

       Alpha-pinene resins

       Physical characteristics of resins

       Pressure sensitive adhesives

       Hot melt adhesives

       Analytical methods

       Commercial resins and their uses

       Commercial production

       Applications in pressure sensitive adhesives

       Applications in hot melt adhesives

25.    Starch Adhesives                                                        

       Introduction

       Unmodified Starches

       High Strength Adhesive

       Cheap Diluted Adhesive

       Non-weather Proof Corrugated Board Adhesive

       Water Resistant Corrugated Paper Box Adhesive

       Final Mixture

       Acid Modified or Thin Boiling Starch Adhesive

       Oxidised Starch Adhesives

       Dextrin Based Adhesives

       Properties

26.  Acrylic Adhesives and Sealants                                    

       Polymerization

       Solution Polymerization

       Properties of the product

       Emulsion polymerization

       Properties of the dispersion

       Properties

       Formulations and Applications 

       Adhesives to paper coated with PVDC

       Delayed tack adhesive

       Adhesives for Laminating

       Laminating Plasticized PVC film to textiles

       Laminating PVC film to particle board

       Laminating plasticized PVC film to split leather

       High temperature &pressure lamination

       Flocking Adhesives

       Building Adhesives

       Adhesives for plasticized PVC floor tiles

       Adhesives for ceramic tiles

       Pressure-Sensitive Adhesives

       Flame Resistant & Pressure Sensitive Adhesive

       Acrylic Sealants

       Aqueous Acrylic Sealants

       Solvent-Based Acrylic Sealants

27.  Pressure Sensitive Adhesives                                     

       Adhesive Strip for Antomotive Trim

Eva-Trialkyl Cyanurate Copolymer Adhesive

       Carboxylate Polymer Based Adhesives

       Fumaric Diester Vinyl Acetate Polymer

28.  Hot melt Adhesives                                                      

       Introduction

       Advantages

       Disadvantage

       Formulations

       Ethylene-vinyl Acetate

       Amorphous polypropylene and Petroleum Resin

       Isopropenyltoluene Copolymers as Tackifiers

       Chlorinated Polyphenyl, Chlorinated
             Polyisoprene and Nitroso Compound

       Carpet Backing Formulation

       Other Polyolefin Compositions

       Amorphous Polyolefin and Styrene Butadiene
             Block Copolymers

       a-Methylstyrene Tert Butyl Styreneolefin terpolymers

       Alkoxystyrene-Acrylonitrile, Copolymers

       Boric Acid as Viscosity Stabiliser in Ethylene-
             Propylene Adhesives

       Thermoplastic Polymer and Chelate of Aminoacetic
             Acid

       Coal Tar Pitch and Ethylene-Acrylic-Acid Copolymer

       Water-Moistenable Vinyl Pyrrolidone-Vinylacetate
             Product

Resins

  1.  Alkyd Resins                                                                 

       Introduction

       Classification

       Synthesis

       Etherification

       Addition reactions of unsaturated monobasic
             fatty acids

      Addition reactions with other unsaturated alkyd                                                                 

            ingredients

       Reactions during coating formation with drying

            alkyds

       Reactions during coating formation in alkyd blends

       Raw materials

       Manufacture

       Health and Safety

       Quality Control and Specifications

       Analysis

       Calculations

       Uses

       Use of Alkyds in Trade-Sales Finishes

       Methods of Analysis

       Determination of Composition

       Chemical Methods

       Determination of Properties and Impurities

  2.  Acrylic Modified Alkyd Resins                                   

       Traffic paints

       Industrial applications

       Conclusion

  3.  Alkyd-Amino Combinations Based on Neem Oil

       Aim of present investigation

       Uses of oils in surface coatings

       Neem oil

       Alkyd resins

       Amino resins

       Experiments & Results

       Preparation of alkyd resin

       Alkyd resin preparation

       Preparation of amino resin

       Testing of performances of resin samples

       Discussion

       Analysis of neem oil

       Preparation of alkyd from neem oil

       Preparation of urea formaldehyde resin

       Preparation of thiourea formaldehyde resin

       Preparation of various samples (mixtures)

       Performances of various resin samples

       Scratch hardness

       Conclusion

4.    Amino Resins                                                                 

       Introduction

       Raw materials

       Chemistry of resin formation

       Typical resin formulations and techniques

       Urea formaldehyde resins

       High solids urea-formaldehyde adhesive resin

       Protective coating resin with high mineral spirits
             tolerance

       Methylated urea formaldehyde textile resins

       Urea-formaldehyde particle board adhesive

       Melamine-formaldehyde resins

       Butylated melamine protective coating resin

       Chlorine resistant melamine resin

       Trimethoxymethyl melamine

       Hexamethoxymethyl melamine

       Melamine resin molding powder

       Melamine resin acid colloid

       Control of the extent of the reaction

       Free formaldehyde estimation

       Viscosity tests

       Solubility tests

       Cure tests

       Urea versus melamine resins

       Package stability

       Competitive product analysis

       Chemical modification for water soluble products

       Chemical modification for oil soluble products

       Ethyleneurea

       Methylated uron textile resins

       Uron resins

       Glyoxal resins

       Miscellaneous resins

       Amino resins in the paper industry

       Formulations for regular and HE colloids

       Toxicity

       Methods of Analysis

       Competitive Product Analysis

5.    Carbohydrate Modified Phenol-formaldehyde         
       Resins                                                                             

       Introduction

       Research on Carbohydrate Modified Resins

       Carbohydrate-Modified Base-Catalyzed PF resins

       Bonding Veneer Panels

       Bonding Flakeboard Panels

       Carbohydrate-Modified PF Resins Cured at
             Neutral Conditions

       Bonding Veneer Panels

       Color of Bondline

       Conclusions

  6.  Epoxy Resins                                                                 

       Introduction

       Synthesis of Resin Intermediates

       Cycloaliphatic epoxies

       Epoxidized polyolefins

       Epoxidised oils and fatty acid esters

       Aliphatic-cycloaliphatic glycidyl type resins

       Epoxy novolac resins

       Resins from phenols other than bisphenol A

       Resins from aliphatic polyols

       Resins from long chain acids

       Fluorinated epoxy resins

       Epoxy resins from methylepichlorohydrin

       Miscellaneous epoxy resins

       Epoxy esters

       Water borne epoxy resins and derivatives

       Diluents and modifiers

       Epoxide reactions and curing mechanisms

       Curing of epoxy esters

  7.  Photographs of Plant & Machinery with Supplier’s Contact Details         

 

 GLUES OF ANIMAL ORIGIN

Animal glues are essentially natural high-polymer proteins.

These organic colloids are derived from collagen which is the

protein constituent of animal hides, connective tissues, and

bones. There are two principal types of animal glues, hide and

bone, differing in the type of raw materials used. In both cases,

animal glue is obtained by hydrolysis of the collagen in the raw

material.

Animal glues find application in a wide range of industrial

uses. They are used in woodworking for such applications as

assembly, edge gluing, and laminating. In the paper industry,

they are used as sizing materials and as binders in paper coating,

and also for paper creping. Animal glues find wide use during

paper manufacture for the retention and recovery of paper fibers

and pigments.

The coated abrasive industry uses animal glues in the

manufacture of abrasive paper and cloth. Closely allied with the

coated abrasives is the use of animal glue in preparation of

compounds for coating wheels, discs, belts, etc.

Animal glues are widely used in the manufacture of gummed

papers and tapes and in paper and paperboard converting.

Animal glues and glue-based compounded products are used

in paper containers—set up and folding boxes, spiral and

convolute tube winding, and laminating. Applications in

bookbinding, magazine and catalogue production, and allied fields

include binding, casemaking, padding, looseleaf binders, and

various luggage and case covering applications.

Animal glues are employed as warp sizing, throwing, and dyeleveling

agents in the textile industry. They are used in the

match industry for match-head compositions. Other uses include

paper gaskets, cork compositions, rubber compounding,

compositions for printing, coating and graining rollers, mining,

ore refining, and metal plating.

Glue molecules consist of amino acids connected through

polypeptide linkages to form long-chain polymers of varying

molecular weights. In hot aqueous solution the glue molecules

take up random configurations of essentially linear form. A wide

range of molecular weights, varying from 20,000 to 250,000 have

been reported. Acidic and basic sites on the amino acid side

chains and terminal groups affect the interactions among the

protein molecules and water, and are believed to be responsible

for the gelation and rheological properties of animal glues.

Because of the presence of both acidic and basic functional

groups in the protein molecule, the molecules are amphoteric

and can bear either a positive or negative charge. Animal glues

can act either as acids or bases depending upon the pH in water

solution. In acidic solution, the protein molecules have an

overall positive charge and function as cations, in alkaline

solution the molecules are negatively charged and behave as

anions. The point where the net charge on the protein is zero

is known as the isoelectric point (IEP). The isoelectric point of

animal glues usually lies in the pH range of 4.5-5.6. Glues in

solution at pH values lower than their IEP have cationic

characteristics while they have anionic characteristics at pH

values above their IEP. Many properties of glue solutions, such

as viscosity, solubility, gel strength, and optical clarity, pass

through a maximum or minimum at this point.

Commercial animal glues are dry, hard, odorless materials

available in granular or pulverized form which vary in color from

light amber to brown. They may be stored indefinitely in the dry

form.

The density of dry animal glue is approximately 1.27 g/ml.

A moisture content range of 10-14% is considered normal for

the commercially dried product. Inorganic ash content, consisting

mainly of calcium salts, may vary from 2% to 6%. Hide glues

are generally neutral in water solution with a usual pH range of

6.5-7.5, and bone glues are slightly acidic with values in the pH

range of 5.5-6.5.

Animal glues are soluble only in water. They are insoluble

in oils, greases, alcohols, and other organic solvents. When

placed in cold water, the glue particles absorb water and swell

to form a spongy gel. When heated the particles dissolve to form

a solution. When the solution is cooled the glue forms an elastic

gel. This property is thermally reversible, and upon application

of heat the gel liquifies. The gelling or melting point of an animal

glue solution will vary from below room temperature to over 120ºF,

depending upon glue grade, concentration, and the presence of

modifiers.

Viscosity in solution and the gel-forming characteristic when

cooled are important properties of animal glues, especially in

adhesive and sizing or coating applications. These properties vary

with the degree of hydrolysis of the collagen precursor and have

a marked bearing on working properties. Animal glues are graded

as to viscosity (fluidity) and gel strength (stiffness of gel

formation) under standard conditions and are available in a wide

range of viscosities and gel strengths.

Animal glues are compatible with and may be modified by

such water soluble materials as glycerin, sorbitol, glycols, sugars,

syrups, and sulfonated oils to act as plasticizers and modify the

working properties of the glue. A degree of moisture resistance

and increase in the solution melting point of animal glues may

be imparted by the proper use of such materials as aldehyde

donors and metal salts.

Since they possess amphoteric properties, animal glues are

highly effective with suitable modification as colloidal flocculants

or suspending agents.

Methods of Manufacture

Both major types of animal glues are prepared by the

hydrolysis of collagen and differ mainly in the type of raw material

used and the manufacturing processes employed.

Hide glues are prepared by initially washing the raw material

with water, followed by curing in a calcium hydroxide (lime)

solution which conditions the collagen for subsequent glue

extraction by hydrolysis. The cured stock is then washed, treated

with dilute mineral acid, such as sulfuric, sulfurous, or

hydrochloric, for pH adjustment, followed by a water rinse. The

stock is then transferred to extraction kettles or tanks and is

heated with water to extract the glue. Several hot water

extractions are made until the glue is completely removed from

the stock.

Dilute glue solutions are filtered, concentrated by vacuum

evaporation and dried. The dry product is ground to the desired

particle size.

Bone glues are made from the collagen occurring in animal

bones. Green bone glues are prepared from fresh bones and

extracted bone glues from bones which have been degreased

prior to processing for glue.

Both types of bone glues are initially conditioned by cleansing

with water and/or dilute acid solutions. The glue is extracted

in pressure tanks with a series of steam and hot water

applications. The dilute glue solutions are filtered or centrifuged

to remove suspended particles and free grease, followed by

vacuum evaporation, drying, and grinding.

Animal glues contain preservatives added during

manufacture to provide adequate protection under conditions of

normal usage and may contain foam control agents, depending

upon the end use.

Commercial Grades and Specifications

Animal glues are graded according to standard methods

developed and adopted by the National Association of Glue

Manufacturers (NAGM). Grades are based on gel strength and

viscosity values.

It is common to market animal glue under brand names or

grade designations identified by the midpoint gram values shown

in Table 1 or by National Association of Glue Manufacturers’

grade number.

Table 2 lists the typical properties of hide and bone types

of glues.

Viscosity of animal glue solutions vary over a wide range,

depending upon grade, concentration, and temperature. Table 3

lists typical viscosity values at 140ºF for a range of dry glue grades

at various concentrations.

CASEIN GLUES AND ADHESIVES

Introduction

Casein is milk protein, obtained from skimmed milk by

precipitation with sulphuric, hydrochloric or lactic acid, to a pH

of about 4.5.100 kgs. of milk usually yields about 3 kgs. of casein.

The precipitated casein is filtered, washed thoroughly, ground

and screened to get 20 mesh or finer product for glue

manufacture. Commercial casein contains about 80-90 per cent

of protein, 1-4 per cent ash, 0-1-3 per cent of butter fat, 7-10

per cent moisture, 0-4 per cent lactose and 0-3 per cent acids

expressed as lactic acid. The composition and amounts of

impurities depend on, among other factors, the method of

manufacture. Reunet casein is not, as it is, suitable for glue

manufacture due to high ash content.

Properties

Casein is an off white powder. Its molecular weight is about

13000-19,000. It is insoluble in water at its isolectric point pH

4.6; the solubility increasing acidity or alkalinity, in the latter

it is more readily soluble. Fixed alkalies like sodium hydroxide,

remain in the glue line as sodium caseinate, a soluble salt while

calcium hydroxide on which water-resistant wood glues are

based, forms insoluble calcium caseinate in the glue line.

Similar insoluble caseinates are formed by zinc, chromium and

aluminium salts etc. Casein powder has a shelf life of above 1

year at 20ºC.

Casein adhesives are unsuitable for outdoor use although

they are more resistant to temperature changes and moisture than

other water-based adhesives. Resistance to dry heat up to 70ºC

is good, but under damp conditions the adhesives lose strength

and are subject to biodeterioration. Their resistance to organic

solvents is generally good. Casein adhesives are often compounded

with materials such as latex and dialdehyde starch to improve

durability. Strong alkaline nature of mixed casein adhesives often

affects the bonding of timber with high resin or oil content by virtue

of a saponification action on poorly wetting surface contamination.

Resultant bonds may be stronger than those obtained from

synthetic resins. Hard woods are subject to staining. Gap-filling

properties are good. Alkaline nature of casein glues precludes the

use of copper or aluminium mixing vessels.

Like animal glues, casein glues have fairly good bond strength

and those containing sodium hydroxide have even better

resistance to water than animal glues; also they recover their

original strength on redyeing. The fact that casein glues do not

gelatinise makes them much easier to handle. The most serious

drawback of casein for use in adhesive is the presence of fatty

matter which has a very adverse effect on the tensile strength

of joint made.

Classification of casein glues and adhesives:

Water-resistant Casein-lime Glue

Water-resistant casein glue sets to a gel as the result of a

slow chemical reaction, sodium caseinate gradually converted to

calcium caseinate. Some of the calcium hydroxide in the formula

has produced sodium hydroxide from a sodium salt also in the

formula, dissolving the casein. The chemicals are dry mixed with

casein as a ready mix powder and shipped to the user as a

complete prepared glue for dispersing in water.

Calcium hydroxide when present in excess, shortens the

working life but increases the water resistance of the glue line.

Addition of sodium silicate (silica: soda ratio 3:1) increases the

working life of the glue, at all levels of alkalinity. A simple

formula using lime and alkali is given below. It has good water

resistance, good working life about 7 hours.

Casein Blend Glues

Casein blends with blood are dry powder glues for cold

pressing plywood. The blood constituent in casein glue

contributes quick setting, thus reducing clamp time, and both

dry and wet strengths are improved. These glues are used in

the construction of flush doors, boxes, furniture and other wood

assembly work where dark colour imparted by the blood is

accepted. Blend glues may compromise mixtures of casein with

soyabean meal. This type of blend is a way to the reduction of

the cost.

Lime free Casein Adhesives

Casein solution not involving lime may be used as adhesives

for adherends other than wood. These are prepared by dissolving

casein with sodium salts, which provide a sufficiently medium

alkali to dissolve the casein. Commonly used sodium salts are

borax soda ash, trisodium phosphate, and others. Casein in

solution in strong alkalies, such as sodium hydroxide, and

ammonium hydroxide, also have the adhesive value. Organic

amines dissolve casein and there is some small use of alkyl

amines, ethanolamines and morpholine as the solvent for casein

adhesives. To give limefree casein adhesives some measure of

water resistance, formaldehyde or formaldehyde donor in the

form of resin or hexamethylene tetramine may be added. More

commonly, an oxide or salt of zinc, aluminium or chromium are

added to improve water resistance. A formulation is given below

used for plywood.

 

AMINO RESIN ADHESIVES

Introduction

Amino resins are the condensation products of amino

compound with aldehydes. The most common and widely used

amino compounds are urea and melamine where as formaldehyde

is almost always the aldehyde.

In a poly condensation reaction, a reactant of functionality

greater than two leads to branching and crosslinking. The

resultant three dimensional network can attain greater size

indefinitely, becoming insoluble and infusible. The over all

reaction of amino resin can be described in three stages. The

first stage is the reaction of amino compound and formaldehyde

to a form a methylol derivatives

RNH2+HCHO RNHCH2OH

Urea is tetrafunctional and melamine is hexafunctional.

Theoritically therefore, the initial reaction can lead to the

formation of a tetramethylol derivatives of urea or a hexamethylol

derivatives of melamine, of the ratio of formaldehyde to ammonia

is high enough for urea, formation of a methyl group slows

formation of another. These methylol derivatives are condensed

with the evolution of water of formaldehyde.

The properties of the adhesive intermediates are very much

dependent on the reaction condition. Molecular weight may vary

from a few hundred to a few thousand, with a wide distribution

of molecular size. Characteristic of commercial products are

solubility, viscosity, pH and concentration. The products are

available either in dry form or in aqueous solutions. Urea resin

adhesives are usually marketed in aqueous solution whereas

melamine resin adhesives are available in powder form.

Manufacturing Technology

Fig. 25.1 is a flow chart for the manufacture of amino resin

adhesives. All the commercial processes are batch type. The unit

operations are reflux and condensation, filtration and spray

drying. Because of the corrosiveness of formaldehyde and its

formic acid content, the reaction is usually carried out in a

stainless steel vessel. The reaction vessel is equipped with a

turbine agitator and reflux condenser and jacketed for heating

or cooling.

The order of addition to the reactor is formaldehyde, boric

acid and urea. When all the components are added to the reactor.

pH is adjusted to 7.0-7.8 and the charge is heated to 120ºC.

Disappearance of urea causes the pH to drop to about 4.0. The

reaction mixture is refluxed at atmospheric pressure for 2 hr.

Vacuum is applied and distillation is carried out under vacuum

of 28-29 in. Of mercury, until approximately 33 parts by weight

of water is removed. Then the system is shifted to total reflux

and cooled to about 30ºC. The pH is adjusted to 7.2-7.4 with

sodium hydroxide. The molar ratio: formaldehyde, urea, is

usually 1.75:1 to 2:1 for plywood adhesives.

board applications, to avoid the smell of formaldehyde in the final

product. General practice is about 1.3-1.5 moles of formaldehyde

per mole of urea. The pH is adjusted to 8.5 to 9.0 and the mixture

is heated to the boiling point under agitation. The solution is

refluxed for 40 min and cooled. The pH is then adjusted to

7.0-8.0 with a saturated solution of trisodium phosphate.

Adhesives for Hardwood Plywood

Plywood is an assembly of an odd number of layers of wood

(Veneer) joined together by means of an adhesive. The difference

between hard wood, plywood and soft wood plywood is that the

former has a ply of wood from the broad-leaf tree, e.g. oak,

walnut, maple etc. where as the veneers for softwood plywood

comes from coniferous trees. Hardwood plywood is generally used

for decorative purposes, softwood plywood for structural purposes.

The adhesive is applied by means of rubber covered rollers in

the glue spreaders. The coated veneers are alternated with the

uncoated veneer in the final assembly. Then the assembled

veneers are pressed in a hot press at approximately 90ºC and

150-300 psi pressure. Press time is about 5-7 min.

Sand Core Binder

Cores are projections of sand in the mould cavity for the

purpose of marking holes in the casting. After casting, the cores

are surrounded by metal and should be removed without

damaging the casting. Urea resins are capable for forming

mechanically strong cores.

PHENOLIC RESIN ADHESIVES

Introduction

Phenolic resins are the reaction products of phenol or

substituted phenols with formaldehyde. An unlimited variety of

resins are possible depending on (1) the choice of phenol (2) the

phenol: formaldehyde molar ratio (3) the type and amount of

catalyst used (4) the time and temperature of the reaction.

Resole resin

The active positions on the phenol molecule are the two

ortho and one para positions. When there is more than one mole

of phenol in the presence of an alkaline catalyst, resole is

formed. The amount of heat determines the final form of product,

e.g., whether the resin is of low viscosity, water soluble liquid

or a grindable solid. If the reaction is carried too far, the resole

can gel. Therefore the reaction is always conducted under

carefully controlled conditions of time, temperature, pH and mole

ratio of formaldehyde to phenol.

Novolac Resins

The reaction of one mole of phenol with less than one mole

of formaldehyde, under acid conditions, results in a novolac

resin. Novolac resin contains methylene links and are phenol

terminated. Methylol and methylene ester groups that are

present in resole resins are absent in novolac. Therefore, this

type of resin is incapable of further reaction without the addition

of more formaldehyde. This is accomplished by the addition of

hexamethylene tetramine, which is known as “hexa”. Hexa

makes the non-heat-reactive thermoplastic novolac capable of

reacting under heat to a cross linked advantage that novolac

resins have over resoles is that no water of reaction is evolved

during cure with hexa. Molecular weight of phenolic novolacs are

in the 500-900 range.

Manufacture

A typical phenolic resin is made by a batch process in a

jacketed stainless steel reaction kettle, equipped with anchor

type agitator and condenser. Molten phenol and formaldehyde

(37-40%) are charged into the kettle and agitation begin. For a

novolac, an acid catalyst is added and steam is introduced into

the jacket to heat the batch with atmospheric reflux. The reaction

is continued for 3-6 hrs at 100ºC. The reaction time is dependent

upon pH and phenol: formaldehyde mole ratio. Following the

reaction period, the batch is dehydrated under atmospheric

pressure and than vacuum. If the resin is to be solid in solution,

the solvent is slowly added to the molten resin in the still,

cooled by refluxing and discharged into drums. Most of the solid

resins discharged into pans are pulverized and blended with

hexa before packaging.

To make resole resin, an alkaline catalyst such as sodium

hydroxide is added to the phenol and formaldehyde before

heating the batch to 80-100ºC. Reaction times are generally 1-

3 hr. Since resole resin is capable of gelling in the still,

dehydration temperature is kept below 105ºC. By the application

of vacuum solid resoles are discharged into resin coolers. The

low molecular weight, water soluble resins are finished at as

low a temperature as possible, usually about 50ºC, whereas the

less reactive para-substituted resoles can be finished at

temperature as high as 120ºC.

Adhesive Compounding

There are two methods in general used for compounding

polychloroprene/phenolic adhesives. The first method involves

masticating the rubber on a two roll mill to reduce crystallinity

and improve solubility. The time of milling and degree of shear

are frequently used to control adhesive viscosity. The magnesium

oxide and zinc oxide are compounded into the rubber on an

unheated mill. The magnesium oxide is always added before zinc

oxide to preclude premature curing of the rubber. The antioxidant

is also added. The compounded rubber is then dissolved with

the resin in the solvent blend in a cement tub.

Compounders who do not have milling equipment use the

slurry method for adhesive preparation. This method consists

of simply adding of resin, pigments and antioxidants together

with the unmilled rubber to the solvent blend in the cement tub.

Adhesives made from unmilled rubber will be more viscous and

therefore, are usually produced at lower solid content. They will

also have higher initial cohesive strength. Adhesives from milled

polymer are however uniform and retain their uniformity upon

ageing.

Vinyl/Phenolic

Vinyl formal, vinyl acetal, and vinyl butyral may be combined

with phenolic resin to produce tough structural adhesives with

good impact strength, resistance to oil and aromatic fuels and

good salt spray and weathering resistance. The presence of

hydroxyl groups on the vinyl chain makes it likely that

crosslinking occurs between the phenolic resole resin and

hydroxyl groups during elevated temperature cure.

 

ACRYLIC ADHESIVES AND SEALANTS

POLYMERIZATION

All industrial polymerization processes are carried out at an

elevated temperature in the presence of an initiator.

Polymerization can be carried out in bulk, solution, suspension,

or emulsion. The most important processes for producing acrylics

for adhesives-solution and emulsion polymerization are dealt

with here.

SOLUTION POLYMERIZATION

In solution polymerization, the monomer or monomer

mixture is dissolved in a solvent which is relatively inert to free

radicals, e.g., ethyl or butyl acetate, benzene, toluene, petroleum

solvent of ketones; then polymerization is effected at elevated

temperatures in the presence of an initiator such as an organic

peroxide or an azo compound which is soluble in the solvent.

Properties of the product

The type of solvent used has a great influence on the reaction

speed and the molecular weight of the resulting polymer in

solution, because of the different chain transfer activities of the

various solvents. Thus, the viscosity of a polymethyl acrylate

solution, and the molecular weight of the polymer, decreases in

the following order: benzene, ethyl acetate, ethylene dicholoride,

butyl acetate, methyl isobutyl ketone, and toluene. The solvent

with the highest chain transfer activity gives polymers of lowest

molecular weight. The molecular weights of solution polymers

are normally lower than those of emulsion polymers. In selecting

the solvent to be used, consideration must also be given to the

economic and safety aspects.

Emulsion polymerization

The emulsion polymerization, process for homo-and

copolymerization of acrylic compounds is of greater significant

than the solution polymerization process. It is effected in the

presence of emulsifiers and initiators (e.g. alkali persulfaces),

normally in water as the external phase. Suitable emulsifiers

are, for example, alkali salts of longchain aliphatic carboxylic or

sulfonic acids, of sulfated ethylene oxide adducts.

PROPERTIES

At room temperature, the homopolymers of methacrylic and

acrylic acid as well as those of the lower methacrylic acid esters

are hard, nontacky products which are suitable only for special

applications in the adhesives field. Homopolymers of acrylic acid

esters from alcohols with at least 2 carbon atoms, which are

elastic, soft, and partially highly tacky products, are used for a

much larger range of adhesive applications.

Further physical properties of the most important acrylic

homopolymers in comparison to those of polyvinyl acetate are

given in Table 1 (properties increasing in direction of arrow).

FORMULATIONS AND APPLICATIONS

Adhesives for paper converting

The requirements imposed on adhesives for bonding paperto

paper are normally not too severe. Because the absorptivity

and surface condition of paper, animal and vegetable adhesives

can attain satisfactory wetting and encourage and thus yield

adequate bonding strength.

However, since the requirements imposed on the bonding

speed-have increased steadily, they can no longer be met with

adhesives based on natural products. Thus, it was not possible

to design and use modern automatic paper converting machines

until it was discovered that polymer dispersions based on

polyvinyl acetate are suitable for this application. By modifying

these homopolymeric polyvinyl acetate dispersions by adding, for

instance, plasticizers, solvents and resins, it was even possible

to render these adhesives suitable for bonding coated and

lacquered paper and to a certain extent also for bonding paper

to polymer films. The range of application for dispersions

modified in this way is, however, limited by the fact that

plasticizer migration may adversely affect the adhesion and/or

bonded materials. The demand for raw materials and adhesives

with improved specific adhesion therefore increased with the

improvements of the materials used in the paper converting

industry, such as printing, lacquering, application of water vapor

impermeable coatings on paper and board, and the use of polymer

films.

Because of their high specific adhesion to a great variety of

surfaces, polyacrylic acid esters in the form of aqueous

dispersions and organic solutions were found suitable for the

production of adhesives for surfaces which are difficult to bond.

The products in question are either copolymers of acrylic acid

esters with one another, or, especially in the case of packaging

adhesives, copolymers of acrylic acid esters with vinyl propionate

or vinyl acetate i.e. copolymers of vinyl acetate with acrylic acid

esters. Terpolymers produced from acrylic acid, acrylic acid ester,

and vinyl acetate have increased adhesion to metal foils and

various plastics and are therefore used for producing adhesives

for this field of application. Terpolymers of this type are also

very resistant to plasticizer migration, e.g., from plasticized PVC

film.

Flame Resistant & Pressure Sensitive Adhesive

For some applications it may be necessary to use a flame

resistant pressure-sensitive adhesive. Acrylics can be rendered

flame resistant.

Pressure-sensitive acrylic adhesives can normally be applied

by the conventional methods, e.g., direct or reverse roll coating

or by air-knife coating. The adhesive compound is applied either

directly to the final substrate or a release paper. In the latter

case the adhesive on the carrier is dried or crosslinked before

it is transferred to the final substrate. This transfer method is

necessary in those case where the backing material would

deteriorate during the drying or crosslinking process. The transfer

method is, for instance, commonly used for producing decorative

films.

For protecting the adhesive coat of pressure sensitive

adhesive materials during transport and storage, the adhesive

coat except in the case of adhesive tapes in rolls, is usually

covered by a release paper or a release foil, Silicone treated

paper, polyethylene or PVC films are, for instance, suitable for

this purpose. Long-chained acrylates exhibit good release effects.

The release material must not have any adverse effect on the

pressure-sensitive adhesive coating. Undesirable effects can be

obtained when unsuitable silicones are used or when the

silicones are not properly processed.

 

Acrylic Sealants

Linseed oil and bitumen were for a long time the commonest

base materials for building sealants. Further developments in

building construction and the steadily increasing demands on

quality resulted in the development of a number of synthetic

polymers for sealants. The first work on acrylics for building

sealants was carried out in response to the technical and

economic success which was achieved by this product class in

the last 10-15 years in the field of surface coatings, such as

paints. The first serviceable acrylic compounds were placed on

the market in about 1960. In the meantime the acrylics,

particularly the aqueous acrylic dispersions, gained considerable

significance in the production of sealants because of their

outstanding aging resistance and adhesion properties as well

as their favourable price.

It is expected that the increase of the consumption of

aqueous acrylic sealants will be above average in the next few

years. The total consumption of sealants will increase only be

approximately 20% during the same period.

The acrylics used nowadays for sealants are tailor-made

copolymers of acrylic and/or methacrylic acid esters and other

monomers.

Usually several monomers are present in order to achieve

the desired properties, such as elasticity, adhesion, resistance

to UV radiation, resistance to chemicals, and hardness, suitable

polymers are linear polymers, most of which are thermoplastic,

as well as polymers which can be rendered adequately elastic

by cold vulcanization, oxidation, or by the effect of alkaline

substance, such as caustic soda solution, cement, or lime.

Acrylics which can be crosslinked with the aid of oxidative

catalysts or epoxy resins are also well known. The dominating

raw materials for acrylic sealants are based on aqueous acrylic

dispersions.

Solvent-containing products and solvent-free products are

also available on the market. The solvent-free products have

been on the market only for a short time and the experience

gained with them is still inadequate. The solvent-containing

products have been on the market for a long time but they gained

considerable less significance than the acrylic dispersions.

Solvent-containing products are usually 80-90% solutions in

xylene. In the initial stage aqueous dispersions were available

with a solids content of only 50-55%. Dispersions with a higher

solids content, were obtained by improving the polymerization

technique. All acrylics must be modified with fillers and other

aids in order to achieve optimum properties.

Aqueous Acrylic Sealants

Aqueous acrylic sealants are employed mainly for those

applications for which compounds bases on linseed oil, butyl

rubber, or polyisobutylene have been used hitherto, i.e., the

sealing of joints which are subject to little elongation. Viz joints

between curtain walls and door and window frame joints.

In view of the experience gained hitherto, it appears that

the aqueous acrylic sealants are also suitable for joints between

prefabricated concrete building components with a practical

elongation of approximately 10-15%.

Soft acrylic sealants with a high degree of elongation have

already been successfully used for many years for joints between

small building components and special applications, e.g., aerated

concrete.

Even the results obtained hitherto in the trials for expansion

joints, which were commenced some time ago, have been positive

until now. Practice will show whether aqueous acrylic sealants

are in fact suitable for this application.

Harder compounds are mainly used for do-it-yourself

application and for sanitary equipment, e.g., bathtub and

washbasins.

AMINO RESINS

Introduction

Amino resin are manufactured throughout the industrialised

world to provide a wide variety of useful products. Adhesives (qv),

representing the largest single market, are used to make plywood,

chipboard, and sawdust board. Other types are used to make

laminated wood beams, parquet flooring, and for furniture

assembly. Some amino resins are used as additives to modify

the properties of other materials. For example, a small amount

of amino resin added to textile fabric imparts the familiar washand-

wear qualities to shirts and dresses. Automobile tires are

strengthened by amino resins which improve the adhesion of

rubber to tire cord. A racing sailboat may have a better change

to win because the sails of polyester have been treated with an

amino resin. Amino resins can improve the strength of paper

even when it is wet. Molding compounds based on amino resins

are used for parts of electrical devices, bottle and jar caps,

molded plastic dinnerware, and buttons.

Amino resins are also often used for the cure of other

resins such as alkyds and reactive acrylic polymers. These

polymer systems may contain 5-50% of the amino resin and are

commonly used in the flexible backings found on carpets and

draperies, as well as in protective surface coatings, particularly

the durable baked enamels of appliances, automobiles, etc. The

term amino resin is usually applied to the board class of

materials regardless of application, whereas the term aminoplast

or sometimes amino plastic is more commonly applied to

thermosetting molding compounds based on amino resins. Amino

plastics and resins have been in use for the past fifty years.

Compared to other segments of the plastics industry, they are

mature products, and their growth rate is now only about half

of that of the plastics industry as a whole.

Most amino resins are based on the reaction of formaldehyde

with urea or melamine. Although formadehyde combines with

many other amines, amides, or amino triazines to give useful

products, only a few have found commercial utility, and they are

of minor importance compared to the major products based on

urea and melamine. Benzoyuanamine, e.g., is used is amino

resins for coatings because it provides excellent resistance to

laundry detergent, a definite advantage in coatings for automatic

washing machines, dihydroxyethyleneurea is used for making

amino resins that provide wash-and-wear properties to clothing.

Aniline-formaldehyde resins were formerly important because of

their excellent electrical properties, but have been supplanted

by newer thermoplastics. Nevertheless, some aniline resins are

still used as modifiers for other resins. Acrylamide occupies a

unique position in the amino resin field since it not only contains

a formaldehyde-reactive site but also a polymerisable double

bond. Thus it forms a bridge between the formaldehyde

condensation polymers and the versatile vinyl polymers and

copolymers.

Formaldehyde links two molecules together and is hence

diffunctional. Each amino group has two replaceable hydrogens

that can react with formaldehyde and thus is also difunctional.