AU680787B2 - Thixotropic wood adhesive gel - Google Patents

Description

S F Ref: 255929D1

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name and Address of Applicant: rdn, In.eI bordel Chemical, InC.

180 East Broad Street Columbus Ohio 43215 UNITED STATES OF AMERICA Actual Inventor(s): Address for Service: Invention Title: Peter Spi.os Columbus, John Anderson and Yogeshbai Babubhai Patel.

Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Thixotropic Mood Adhesive Gel a t e oa aoo •ooo a oe f a *a The following statement is a full description of this invention, including the best method of performing it known to melus:- 5845 la Thixotropic Wood Adhesive Gel Background Of The Invention Field of the Invention This invention relates to thixotropic, water based, general purpose, polyvinyl acetate, polyvinyl alcohol adhesive gel for porous and semiporous substrates such as paper, card board, cloth and wood.

Background Art Many different general purpose adhesives for adhering porous and semiporous substrates such as paper and wood are available. However, such adhesives have various shortcomings for use in projects which are performed on wall boards and other vertical surfaces such as in a class room by young children such as excessive running when placed on a vertical surface, and difficulty of the dried adhesive: to take a conventional wood stain; to be sanded; or to resist moisture.

This invention provides a thixotropic adhesive gel which can be easily dispensed from a conventional hand held plastic squeeze bottle for wood glue. After being dispensed from the squeeze bottle, the adhesive does not run on vertical surfaces and forms a dry glue line which can be sanded, stained and has resistance to moisture.

The adhesive gels of this invention comprise: water; a partially hydrolysed polyvinyl alcohol; a water-soluble thickening agent polymer which is compatible with polyvinyl alcohol; a water-soluble defoamer; and a water-soluble plasticiser for the polyvinyl alcohol which does not destroy the clarity of the gel. Additional conventional ingredients used in adhesive compositions such as preservatives and the like can also be used provided that as• such ingredients or the quantity thereof do not adversely affect the adhesives. Compatible preservatives are generally added to the gel.

The Handbook of Water-Soluble Gums and Resins by R.L. Davidson, 1980 (McGraw-Hill, Inc.) page 20-20 discloses partially hydrolysed polyvinyl alcohol as an adhesive and page 20-18 discloses the use of certain gelling agents to control penetration of polyvinyl alcohol solutions into porous substrates or to prevent run-off of coating by dipping whereas page 20-19 of that reference discloses the use of an antifoam agent with 30 polyvinyl alcohol. Pages 21-15 and 21-16 of the Handbook reference describe adhesive properties of polyvinylpyrrolidone (PVP). Among other shortcomings, these references do not mention the use of thixotropic agents with polyvinyl alcohol nor proportions of ingredients used in obtaining the advantageous properties of this invention.

Water based polyvinyl acetate emulsions are popular wood glues. The Handbook of 35 Adhesives, Third Edition which is edited by I. Skeist: pages 388-390 describes the use of polyvinyl alcohol for imparting wet tack and as a protective colloid for polyvinyl acetate S .emulsions; pages 394-395 discusses thixotropy, pseudoplasticity and thickening of 1N:\LIBZI256929D1:SAK polyvinyl acetate with various materials; and page 398 describes the use of foam control agents and biocides in such adhesives.

US 3 442 845 relates to polyvinyl acetate adhesives which, upon drying, are redispersible in cold or hot water. The adhesive compositions of the 845 patent use polyvinyl alcohol, water-soluble gums, and cellulose ethers as anti-coalescing agents for the polyvinyl acetate. Propylene glycol and other polyhydroxy compounds are mentioned as plasticisers for polyvinyl alcohol.

US 4 251 400 also relates to a polyvinyl acetate adhesive which is redispersible in hot and cold water in the dried film form and which uses polyvinylpyrrolidone and a nonvolatile, water-soluble, plasticiser as the anti-coalescing agent. In addition to the polyvinyl acetate and polyvinylpyrrolidone that patent also mentions the use of polyvinyl alcohol, propylene glycol, as well as water-soluble ethers in the adhesive composition.

European Patent Application Publication Number 0210052 relates to various tubes for dispensing reactive adhesives such as cyanoacrylate at a rate of one or two drops at a time. The patent mentions resilient plastic tube dispensers and broadly states that the adhesive can be thixotropic.

Technical Bulletin DB-15 entitled "KELZAN, Xanthan Gum", of Merck Co.

describes xanthan gum as a thickener and suspending agent for water based systems and promotes its suspending, pseudoplastic (thixotropic), and stability properties.

KELCO XANTHAN GUM, Third Edition, of Kelco a division of Merck Co.

shows much the same as the above KELZAN bulletin, and also states that its xanthan gum provides smooth flow under sheer in adhesive formulations and that this allows the application of high solids.

US 3 676 174 Uses a mixture of wood flour and plaster of Paris to form a paintable 25 base for moulded articles. In Col. 2, step 5, it discloses a composition of: 1 part plaster of Paris; 1 part of wood flour; and 6 parts fine metal powder. This dry powder is mixed with an equal quantity of polyvinyl acetate solution diluted with water and is used as a coating on clay objects.

US 2 510 257 discloses an aqueous polyvinyl acetate emulsion adhesive containing glyoxal and polyvinyl alcohol. The glyoxal imparts water resistance to the adhesive.

US 4 638 022 uses polyvinyl acetate together with pecan shell flour to provide a coating for wood or plastic which accepts conventional wood stains. The composition of this reference appears to be in an organic solvent system.

S* A commercial product called "Glue Gap 202 GF Filling" of the Garott Wade Company, Inc. which is located at 161 Sixth Avenue, New York, N.Y. is an aqueous polyvinyl acetate emulsion adhesive which contains wood fibres or wood flour. This product is viscous but has little or no thixotropy; also, much of the wood fibre appears to settle easily and requires shaking to disperse the wood fibres.

[N:\LIBZI255929D ISAK Summary Of The Invention According to a first embodiment of the present invention there is provided a clear, thixotropic adhesive gel comprising a major quantity of water; partially hydrolysed polyvinyl alcohol in an amount sufficient to provide fibre tearing bonds on paper after drying; a water-soluble plasticiser in an amount sufficient to plasticise the polyvinyl alcohol; a water-soluble defoamer in an amount sufficient to prevent air bubbles from destroying the clarity of the gel; a water-soluble thickening agent polymer which is compatible with the polyvinyl alcohol, said thickening agent being in an amount sufficient to provide a thixotropic index and viscosity allowing extrusion of the gel from a flexible lo dispenser having a dispensing opening of about 1.85mm in diameter by applying fingerpressure to the dispenser while, upon extrusion, the gel forms a bead which does not run when applied in a horizontal line on paper in a vertical plane.

According to a second embodiment of the present invention there is provided a clear adhesive gel comprising about 70% to 93% of water; about 5% to 25% of partially hydrolysed polyvinyl alcohol; about 0.5% to 1.5% of xanthan gum; about 0.5% to 3% of a water-soluble plasticiser for the polyvinyl alcohol; and about 0.05% to 0.35% of a watersoluble defoamer.

According to a third embodiment of the present invention there is provided an article of manufacture comprising: a flexible dispenser wherein the dispenser has a dispensing opening of from about 7.1 to 77.5mm 2 contains a clear adhesive gel which can be dispensed therefrom by finger-pressure to form a glue line which does not run when extruded on paper in a vertical position; and said adhesive gel consisting essentially of a major quantity of water; partially hydrolysed polyvinyl alcohol in an amount sufficient to form fibre tearing bonds on paper upon hardening; a water-soluble thickening agent polymer compatible with the polyvinyl alcohol and in an amount sufficient to provide the adhesive gel with a thixotropic index and viscosity which permit extrusion of the adhesive from said opening in a steady stream by use of finger-pressure to form a horizontal glue S line which does not run when placed un paper in a vertical plane; a water-soluble plasticiser which is compatible with the polyvinyl alcohol in an amount sufficient to plasticise the polyvinyl alcohol; arad a water-soluble defoamer in an amount sufficient to prevent entrapped air from destroying the clarity of the gel.

Advantages of the invention include: The adhesive gel will not run when applied to porous and semiporous vertical surfaces and will not spill when used as a general purpose school glue. The adheive gel extrudes easily and in a steady stream from a small orifice when a flexible tube or squeeze bottle is finger pressed and reverts to gel when finger-pressure is released. The combination of adhesive gel and small dispenser.

opening, eg. from about 1.52 to, 29.21mm in diameter, minimises or eliminates wrinkling of paper upon drying of the adhesive. The adhesive in a clear resilient plastic dispenser can be viewed within the dispenser as clear which may include a tint of colour. The "'4'^o"adhesive gel is preferably crystal clear or has a clear coloured tint and provides a clear dry (NALBZ255929D1;SAK film. The dry adhesive film is flexible and will not crack on bending. The adhesive gel has a strong wet-tack to hold paper surfaces together while drying. It has a long rate of set so as to permit sliding and positioning of substrates before fibre tearing permanent adhesive bonds are developed. The adhesive gel as well as dried films thereof will launder-out in hot or cold water. (10) The adhesive gel can be tinted easily with non-toxic water-soluble dyes. (11) The adhesive gel is non-toxic and is not an irritant to the skin and eyes as defined in the United States Federal Hazardous Substances Act.

Brief Description of the Drawings Figure 1 is a side elevation of a flexible tube dispenser containing the adhesive gel of this invention.

Figure 2 is a plan view of that shown in Figure 1.

Figure 3 is a side elevation of a flexible squeeze bottle containing the adhesive gel of this invention.

Figure 4 is a plan view of that shown in Figure 3.

Detailed Description Of The Invention Figure 1 shows a conventional, flexible plastic, low density, polyethylene tube dispenser (10) having a clear hollow tube portion (12) which has a capacity of about and a crimped, closed end The wall thickness of the polyethylene is 0.5mM. The closed end beyond crimp (14) has an extending flap (16) which has a cut out portion (18) so that the dispenser (10) can be hung up and displayed or stored. The dispensing end of tube (12) has a conventional screw threaded dispenser closure cap (22) which can effect opening and closing of orifice (26) by holding cap (22) in place while twisting cap end Dispenser (10) contains adhesive gel (40) of this invention and the adhesive (40) in contact with tube (12) provide a clear appearance when the dispenser is viewed.

Figure 2 more clearly shows dispenser opening (26) at the end of cap (24).

Figure 3 shows a clear, conventional, flexible plastic, low density polyethylene squeeze bottle (30) which has a capacity of 120mL. Bottle (30) has neck portion (32) which has an open end with conventional screw threads, not shown. Conventional 30 dispenser closure cap (22) has internal screw threads which mate with those of neck portion Cap (22) can effect opening and closing of orifice (26) by twisting of the cap end (24) as with Figures. 1 and 2. Dispenser bottle (30) contains clear gel adhesive The clarity or transparency of the portion of the bottle (30) containing the adhesive (40) is similar to that of Figure. 1.

Figure 4 more clearly shows dispenser opening (26) at the end of cap (24).

In place of a flexible plastic tube or squeeze bottle, other dispensers such as deformable, ductile, metal tubes can be used; although such tubes do not provide for clarity.

[N:\LIBZI255929D1:SAK The preferred polyvinyl alcohol adhesive gels of this invention are clear. The term "clear" is used herein in contrast to opaque. The term "clear" includes transparent, ie., see through, as well as translucent.

The term "water-soluble" as used herein refers to solutions of either solids or liquids which are soluble or miscible in water to provide a solution which is clear at the concentration employed.

The term "thixotropic" as used herein is also meant to cover pseudoplastic. The thixotropic index used in this invention permits extrusion of the gel from a small dispenser opening by use of finger-pressure on a flexible dispenser such as a tube or squeeze bottle.

Due to thixotropy, the adhesive rapidly reverts to a higher viscosity after extrusion from the orifice when force or shear is not being applied. The adhesive gel does not run, when applied to wood in a vertical plane after being extruded through the small orifices of the dispensers used in this invention. By not running, the adhesive fairly stays in place on the area to which it is extruded with minimal spreading unless external force is applied. The minimum spreading can include a slight amount of downward creep due to gravity such as that of less thanrmm and preferably less than 2.54mm. The use of smaller orifices in the dispensers such as those of less than 2.54mm in diameter, eg., 18.5mm in diameter minimise any creep.

The thixotropic index for the adhesive gel of this invention varies from about 1.5 to 4.5 preferably about 1.5 to 4 and particularly 1.8 to 2.5. The term "thixotropic index" as used herein is the number obtained by dividing the viscosity reading of the gel at 2rpm in centipoise by the viscosity reading at 20rpm in centipoise by use of an RVF Brookfield viscometer using a number 6 spindle at 25 0

C.

The viscosity readings in this invention are taken after the gel has been at rest eg.

a 25 undisturbed, for a period of time such as 12 hours. The adhesive gels of this invention are stable.

In order to prevent running after being extruded from a squeeze bottle, the adhesive of this invention has a high viscosity at rest or under low shear. However, due to its thixotropic properties it will pour out of an open mouth container or flow to a lower level when the container is tipped. This facilitates the discharge of the adhesive from plastic bottle glue dispensers having small openings. On the other hand, a non-thixotropic adhesive or adhesive with little thixotropy at the viscosities used in this invention present difficulties in removal from a plastic bottle having a small orifice and particularly in Sremoval of substantially all of the adhesive.

The polyvinyl alcohol adhesive gels of this invention have a viscosity of about 30 000cps to 100 000cps at 25 0 C and preferably about 50 000cps to 90 000cps at 25°C as measured with an RVF Brookfield viscometer by use of a number 6 spindle at 2rpm.

When measured at 20rpm with an RVF Brookfield viscometer at 25 0 C by use of a number 6 spindle, the viscosity of about 15 000cps to 60 000cps, preferably about 20 000cps to -4o 40 000cps, provided that the thixotropic index is within the ranges set forth herein.

ne rne 1N;:\LBZI255929D1:SAK 6 The gel of this invention has good wet tack properties. It has a slow enough rate of set that permits a sufficient period of time for positioning a second piece of wood such as by sliding of the second surface over the first before wood fibre tearing adhesive bonds develop between the two substrates which permanently hold the pieces in place.

Water The major ingredient in the polyvinyl alcohol adhesive gel of this invention is water.

The quantity of water can vary over a broad range such as that from about 70% to 93 by weight of the adhesive gel, preferably 75% to 93% and particularly from about 80% to by weight thereof.

The total quantity of water includes additional quantities of water added in the preparation of the adhesive as well as that carried by the component ingredients.

Polyvinyl Alcohol Adhesive Polymer The adhesive agent used in this invention is partially hydrolysed polyvinyl alcohol or such polyvinyl alcohol with polyvinylpyrrolidone (PVP) wherein the PVP replaces up to about half of the polyvinyl alcohol. The polyvinyl alcohol will normally have a molecular weight of about 25 000 to 100 000 and preferably about 40 000 to 80 000. The viscosity of the polyvinyl alcohol can vary over a wide range such as that of about 5 or 6cps, which is referred to in the art as low viscosity, to 40 to 50cps, which is referred to in the art as high viscosity as measured with an LVF Brookfield viscometer using a number 1 spindle at 60rpm at 20 0 C for a 4% aqueous solution. The preferred degree of hydrolysis for the partially hydrolysed polyvinyl alcohol is 87% to 89%.

The PVP can have a molecular weight, expressed as a K value, which varies over a wide range such as that of a K value of about 26 to 100.

The quantity of polyvinyl alcohol or polyvinyl alcohol together with PVP in the gel 25 can vary over a wide range such as that of from about 5% to 25% by weight of the 000 adhesive gel, preferably from about 5% to 20% and particularly 10% to 15% by weight of the adhesive gel.

Plasticisers too A water soluble plasticiser for the polyvinyl alcohol is also used in the composition.

Such plasticisers soften the polyvinyl alcohol and make the polyvinyl alcohol more flexible.

0 Illustrative of such plasticisers there can be mentioned: alkanols having from 2 to 5 carbon atoms and 2 to 3 hydroxy groups such as: propylene glycol; glycerol; ethylene glycol; and diethylene glycol; although ethylene glycol and diethylene glycol can have some toxic properties. The quantity of the water-soluble plasticiser is that which is sufficient to plasticise the polyvinyl alcohol and will genera!'y vary from about 0.5 to 3% by weight of the adhesive gel. Although such plasticisers can be used it is preferred to avoid them when o: higher water resistance is desired.

IN:\LUBZ1255929D1 SAK The Water Soluble Thickening Agent Polymer The thickening agent polymer can be any water-soluble thickener polymer which is compatible with polyvinyl alcohol and which imparts thixotropic or pseudoplastic properties within the thixotropic index and viscosity ranges of the adhesive gels of this s invention. By "compatible" we mean miscible in that it does not cause separation of the ingredients in the gel. Illustrative of the high viscosity thickening agent polymer there can be mentioned the sodium salt of carboxymethylcellulose, also referred to herein simply as CMC, sodium alginate, and xanthan gum. The quantity of the thickener is that which is sufficient to provide the adhesive gel with the desired thixotropic index and viscosity.

Such quantity will generally vary from about 0.5% to 1.5% by weight of the adhesive gel and preferably from 0.85% to 1.25% by weight of the adhesive gel.

The Water-Soluble Defoamer Conventional water-soluble defoamers are generally used in the adhesives of this invention. Such defoamers include silane defoamers and polyalkoxylated polyethers eg., butoxy polyoxyethylene-propoxyl propylene glycol. The quantity of the defoamer is that which maintains density of the gel, prevents excessive foam in the manufacturing process, and facilitates filling of the dispensers with the gel. Generally, the quantity of the defoamer varies from about 0.05% to 0.35% by weight of the gel composition.

The Dispenser The dispenser for the thixotropic adhesive gel can be a conventional, flexible, low density polyethylene squeeze bottle such as one having a capacity of 120mL. Illustratively, the 120mL plastic squeeze bottle used for ELMER'S SCHOOL GLUE of Borden, Inc. is suitable. Such dispensers are shown in Figures 1 to 4 hereof. Finger-pressure between the thumb and forefinger or the thumb and fingers is used to dispense the gel from the 25 dispenser squeeze bottle on to a substrate such as wood. The dispenser cap orifice (26) has a diameter of about 1.52 to 2.92mm, preferably 1.78 to 2.54mm and particularly about 1.78 to 2.0mm. The use of a rectangular slit of approximately 1.6mm wide and 7.94mm long as found in many wood glue dispensers is also suitable. The thixotropic gel adhesive (40) flows out of the cap orifice (26) in a steady stream on being finger-pressed due to its thixotropic properties in spite of its high viscosity in the undisturbed state. The area of such dispenser opening is from about 7.1 to about 77.5mm 2 When applied to a substrate in the vertical plane, the gel does not run and has a minimum amount of creep due to the thixotropic properties of the gel. Any such creep is S* generally less than 3.8mm and more often less than 2.54mm. Due to the ability of the thixotropic gel to be applied through a small dispenser opening, a thin glue line can be provided on a first substrate such as construction paper which minimises the amount of adhesive as well as wrinkling of paper upon drying. When a second substrates such as a second piece of construction paper is pressed over the first piece in order to be adhered

SA

4 ,,Ri thereto, the high tack of the gel holds the second substrate in place on the vertical surface.

D 1oThe slow rate of set permits a prolonged period of time for positioning the second substrate (N:\LIBZ1255929D1:SAK L- I such as by sliding of the second surface over the first before fibre tearing adhesive bonds develop between the two substrates which permanently hold the pieces in place.

In order that those skilled in the art may more fuilly understand the invention presented herein, the following examples are set forth. All parts and percentages-in the examples, as well as elsewhere in this application, are by weight, unless otherwise specifically stated. The viscosity measurements referred to herein are by use of an RVF Brookfield viscometer with a number 6 spindle at 25°C unless otherwise specifically stated. The term "low shear" refers to the viscosity measurements at 2rpm whereas "high shear" refers to viscosity measurements taken at Procedure For Determining Wet Tack This procedure uses blocks of Grade 1 and Grade 2 white pine with each block being long, 19mm high and 45mm wide. The grain of the wood is parallel to the length of the block and the sides which are 19mm high and 50mm long are planed and smooth.

Such sides are referred to herein as test sides. Each test side therefor provides a surface of 19.7cm 2 A series of tests are performed with the above described blocks of wood with two blocks being required for each test. In each test an eye screw is placed in the centre of one of the test sides of each block. Gel adhesive is then placed on the opposite side of the eye screw of one of the test blocks so that it covers the entire 19.7cm 2 of surface, The test side of the second block opposite the second block eye screw and the side of the first block having the glue thereon are pressed against each other in sliding relationship while being placed in register so that the edges of one block do not extend beyond the edges of the other. A scale is attached to the eye screw of the first block whereas a weight is attached to the eye screw of the second block. The scale is then lifted upwardly by the operator and 25 the two blocks are lifted vertically so as to lift the weight. Thus, the operator lifts the scale by hand which in turn lifts the first block through the eye screw. This in turn lifts i: -the second block due to the wet tack of the adhesive which in turn lifts the weight which is attached to the second block eye screw. This test is repeated with clean blocks of wood and the weight is increased each time until the adhesive between the two blocks fails to lift the second block and its attached weight. The last weight which was lifted in this test is referred to as the quantity of wet tack or simply wet tack of the adhesive. This test measures the wet tack in a direction which is perpendicular to the adhered surfaces. In Sspite of the lengthy description of this test, it can be performed, and for reliability is performed, rapidly by the operator. The glue, when the wet track is measured between the 35 blocks of wood is very close to the physical and chemical condition of the glue when it left the dispenser orifice. The wet tack is a measure of what is often referred to as the grabbing power of the adhesive. A minimum amount of wet tack is needed when gluing on substrate to another in a vertical plane, otherwise, the substrate which is not held in place ut rather depends on the wet glue for positioning would slip off of the vertical surface of

C'

[N:\LIBZI255929D1:SAK

I

9 the first substrate. The wet tack of the gel of this invention preferably varies from about 2 to over 90g.cm- 2 and preferably from about 38 to 75g.cm 2 Procedure For Determining Rate Of Set Determinations for the rate of set are performed on a white paper pad. A glue line is placed on smooth white paper of a 13.97 x 21.59mm paper pad. The single glue line is placed in about the middle of the pad parallel to the length of the paper. This glue is then spread evenly by the use of a No. 22, WIRE-CATOR which is supplied by the Leneta Company. The WIRE-CATOR is also referred to as a wire wrap rod. The WIRE- CATOR draws down a uniform thickness of film from the single glue line. Use of the No.

22 WIRE-CATOR draws down a glue line to a thickness of 1.5 mil.

A second sheet of the same paper has one of its narrow ends raised so that it can be grasped by the fingers. The second sheet is pressed over the first sheet. The two pieces are then slowly pulled apart by lifting the raised end of the second sheet and holding the first sheet down in place. The time that it takes to encounter fibre tearing bond is the rate of set. The preferred rate of set for the gels of this invention is from about 16 seconds to seconds and preferably from about 18 to 32 seconds.

The values for both the wet tack and rate of set recited herein are obtained at and a relative humidity of Example 1 This example shows the composition, preparation and properties of an adhesive gel of this invention as well as use of an article of this invention.

6 6 *6* 6@* 4.

6* *6 6 4 0 0 6@* S S 4. 0 4..

S o 0e 6* 04 4 0 4 4 0* Ingredient Parts by Weight Deionised water 83.51 Polyvinyl alcoholl 13.33 Sodium salt of Carboxymethylcellulose 2 1.00

DEFOAMER

3 0.25 Ethyl parahydroxybenzoate 0.05 Benzoic Acid 0.10 Propylene Glycol 1.75 Blue dye 4 0.01 1 VINOL 523 which is a partially hydrolysed polyvinyl alcohol supplied by Air Products and Chemicals, Inc.

2 CMC 7HX4 which is supplied by the Aqualon Company of Wilmington, Delaware.

25 3 DEFOAMER 622 which is a monofunctional polyalkoxylated polyether defoamer supplied by the Thomas W. Dunn Corp of Ridgefield, N.J.

4 No. 5601, FD&C Blue No. 1 which is supplied by Warner Jenkinson Cosmetic Colours of South Plainsfield, New Jersey.

.r (N:\LIBZI255929D1iSAK

P

The adhesive of Example 1 was prepared by slowly adding the polyvinyl alcohol and CMC to water under fast agitation in a jacketed tank equipped with agitators. The CMC is preferably dry blended with a portion of the polyvinyl alcohol before addition to the water.

The defoamer was then added. A small portion of the total amount of water in the gel can be obtained from steam condensation when the mixture is heated in contact with steam, The ethyl parahydroxybenzoate and benzoic acid were then mixed in the composition and the temperature of the mixture was raised to 85 0 C to 90°C with slow agitation for about to 20 minutes until the composition was smooth and homogeneous. The composition was then cooled to 50°C with continued slow agitation. The blue dye was then added which 1 had been prepared in advance by mixing 2 parts of the dye with 98 parts of water. Mixing was continued until the batch colour uniform.

The adhesive was then filled int) 3 fluid ounce clear, low density polyethylene tubes (12) having a cap (22) and nozzle (24) and opening (26) of 0.073 inches in diameter. After filling, the back end of tubes (12) are heat sealed to form a crimp (14) having flap (16) extending therefrom as shown in Figure 1 and Figure 2. The portion of the tube (12) in direct contact with the gel (40) was transparent with a slight blue tint. The portion of tube (12) which was not in direct contact with the gel was translucent.

All of the examples set forth hereinafter were performed in much the same manner as with Example 1.

The adhesive gel of Example 1 was transparent with a blue tint, easily dispensed with finger-pressure from the resilient plastic tube (12) having an orifice (26) of 1.85mm diameter. It had wet tack of 67.43g.cm 2 and a time of set of 25 seconds. It was free of air bubbles, and when dispensed from such tube and orifice on to a sheet of paper held vertically, it formed a uniform, thin, horizontal bead of adhesive which did not run and formed fibre tearing adhesive bonds on drying to a clear film. The gel can be dispensed in a steady stream through the dispenser orifice. The strong wet tack held a second sheet of paper in place on the vertical surface while the lengthy time of set permitted sliding and repositioning of the second sheet on the first before permanent adhesive bonds were formed. The gel washed out of clothing both before and after drying. This product too: exhibited all the advantages set forth in the hereinabove Summary of Invention. It had a thixotropic index of about 2. The viscosity of the adhesive gel when measured at with an RVF Brookfield viscometer with a No. 6 spindle was as follows: 0 pInitially, after manufacture, and at a speed of 2rpm, a viscosity of 50 000 to 000cps.

Initially, after manufacture, and at a speed of 20rpm, a viscosity of 24 000 to 28 000cps.

After standing for about 12 hours and at a speed of 2rpm a viscosity of 70 000 to OOcps.

After standing for about 12 hours and at a speed of 20rpm a viscosity of 30 000 to 4,iopocps.

IN;\LIBZl256929D1 tSAK 'p rr 11 After one month from manufacture, the viscosity was not over 100 000cps when measured at a speed of 2rpm. The adhesive of this invention had a pH of 4.8.

Example 2 This example provides another formulation having the advantageous properties of this invention and illustrates the use of a lower viscosity polyvinyl alcohol. The blue dye, CMC and defoamer were the same as in Example 1.

Ingredient Parts By Weight Deionised water 76.84 Blue dye 0.01 Polyvinyl alcohol* 20.00 CMC Defoamer 0.25 Ethyl parahydroxybenzoate 0.05 Benzoic acid 0.10 Propylene glycol 1.75 VINOL 205 which is a product supplied by Air Products and Chemicals, Inc, This gel had a viscosity of 67 500cps at 2rpm and 21 000 cps at 20rpm when measured at 25°C with a Brookfield RVF viscometer having a No. 6 spindle. The o1 thixotropic index was 2.4 and it had a wet tack of 38g.cm- 2 Example 3 This example illustrates the use of smaller quantities of the polyvinyl alcohol and CMC which oroduced product having the advantageous properties of this invention.

0 6*

S.

*6 *0 p 00 p.

p S p *pp 0**Pa

S.

0 S S; pI p pp P0 i*l p ii Ingredient Parts By Weight Deionised water 85.4 Blue dye 0.01 Defoamer 0.25 Polyvinyl alcohol* 11.6 CMC 0.87 Propylene Glycol 1.75 Preservative** 0.10 VINOL 540 which is supplied by Air Products and Chemicals, Inc. for a partially hydrolysed polyvinyl alcohol having a high viscosity and a percent hydrolysis of 87% to 98%.

KATHON LX 1.5 which is a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one which is supplied by Rohm and Haas Co.

The blue dye, defoamer and CMC used in Example 3 were the saw as that of Example 1.

N:\LIBZI255929D1 :SAK 12 Example 4 This example illustrates the formula of a position of this invention which contains a substantial quantity of polyvinylpyrrolidone.

Ingredient Parts By Weight Deionised water 83.51 Defoamer 0.25 Polyvinyl alcohol 6.67 CMC 1.00 Polyvinylpyrrolidone* 6.66 Propylene Glycol 1.75 Blue dye 0.01 Ethyl parahydroxybenzoate 0.05 Benzoic acid 0.10 LUVISCOL K-90 which is supplied by B.A.S.F. Aktiengesellschaft.

The adhesive gel of this Example 4 had a viscosity of 35 000cps at 2rpm and 000cps at 2rpm when measured by use of a Brookfield RVF viscometer at 25°C with a No.

6 spindle. The thixotropic index was 1.75 and the wet tack was 38g.cm- 2 The polyvinyl alcohol, CMC, and blue dye were the same as that used in Example 1.

Example composition of this invention which used xanthan gum as o1 This example illustrates a the thickening agent polymer.

9 9 .9 9 *9 9 *a Ingredient Parts by Weight Deionised water 83.51 Blue dye 0.01 Polyvinyl alcohol 13.33 Xanthan gum 1 1.00 Defoamer 0.25 Ethyl parahydroxybenzoate 0.05 Benzoic acid 0.10 Propylene glycol 1.75 1 KALZAN, an industrial grade xanthan gum supplied by the Kelco Division of Merck Co.

.9 .9 o g* The gel of Example 5 had a viscosity of 62 000cps and 13 500cps for a thixotropic S 15s index of about 4.6. The viscosity was measured at 25°C by use of a Brookfield RVF o* viscometer with a No. 6 spindle. This product had a wet tack of 62g.cm- 2 IN;\LIBZi255929D1 SAK.

13 Example 6 This example shows the use of sodium alginate as the thickening agent polymer for preparing a gel adhesive of this invention. The remaining ingredients are the same as those used in Example 1.

Ingredient Parts by Weight Deionised water 83.51 Blue dye 0.01 Polyvinyl alcohol 13.33 Sodium alginate* 1.00 Defoamer 0.25 Ethyl parahydroxybenzoate 0.05 Benzoic acid 0.10 Propylene glycol 1.75 KELGIN MV which is supplied by the Kelco Division of Merck Co.

The gel of this Example 6 had a viscosity of 35 000cps and 23 OOOcps when measured at 2rpm and at 20rpm respectively with a Brookfield RVF viscometer at 25 C using a No. 6 spindle. It had a thixotropic index of about 1.5 and a wet tack of 52g.cm- 2 Example 7 This example shows incompatibility of hydroxypropylmethylcellulose as the thickening agent polymer. This formulation was unsatisfactory since a thick layer of the hvdroxvmethyl cellulose separated and formed on top of the sample.

d 9000 a 0**S *9* 9 *0 40 0 0

S*

a 4. 4 0

S

9

S

905 S 9 @9 9 *9 50~ -i 9i 9 9099, Ingredient Parts by Weight Deionised water 83.51 FD&C No. 1 aqueous solution) 0.01 Polyvinyl alcohol 13.33 Hydroxypropyl methylcellulose* 1.00 Defoamer 0.25 Ethyl parahydroxybenzoate 0.05 Benzoic acid 0.10 Propylene glycol 1.75 METHOCELL K 15 MS which is supplied by the Dow the hydroxypropylmethylcellulose, the remaining ingredients Example 1.

Chemical were the Co. Apart from same as that of Example 8 The substitution of hydroxyethylcellulose for the hydroxymethyl cellulose of the formulation in Example 7 also gave unsatisfactory results since a thick layer of the hydroxyethylcellulose separated out of the formula.

IN:\LIBZ1255929DI:SAK

Claims (18)

1. A clear, thixotropic adhesive gel comprising a major quantity of water; partially hydrolysed polyvinyl alcohol in an amount sufficient to provide fibre tearing bonds on paper after drying; a water-soluble plasticiser in an amount sufficient to plasticise the polyvinyl alcohol; a water-soluble defoamer in an amount sufficient to prevent air bubbles from destroying the clarity of the gel; a water-soluble thickening agent polymer which is compatible with the polyvinyl alcohol, said thickening agent being in an amount sufficient to provide a thixotropic index and viscosity allowing extrusion of the gel from a flexible dispenser having a dispensing opening of about 1.85mm in diameter by applying finger-pressure to the dispenser while, upon extrusion, the gel forms a bead which does not run when applied in a horizontal line on paper in a vertical plane.

2. The gel of claim 1 wherein the polyvinyl alcohol is from 5% to 20% by weight of the gel.

3. The gel of claim 1 or claim 2 wherein from 5% to 50% by weight of the polyvinyl alcohol is replaced with polyvinylpyrrolidone.

4. The gel of any one of claims 1 to 3 wherein the quantity of thickening agent is sufficient to provide a thixotropic index of from 1.5 to 4.5 when viscosity of said gel at 20rpm is divided into the viscosity at 2rpm of said gel at 25 0 C as measured with an RVF Brookfield viscometer using a number 6 spindle. 20 5. The gel of claim 4 wherein the thixotropic index, as herein defined, is from 1.5 to

6. The gel of any one of claims 1 to 5 having a wet tack of at least 35g.cm- 2

7. The gel of any one of claims 1 to 6 having a rate of set of 16 to 35 seconds at a temperature of 25 0 C and a relative humidity of

8. The gel of any one of claims 1 to 7 which is transparent.

9. The gel of any one of claims 1 to 8 which comprises 70% to 93% water; to 25% of polyvinyl alcohol; 0.5% to 1.5% of thickening agent; 0.5% to 3% of plasticiser; and 0.05% to 0.35% of defoamer, said percentages based on the weight of the gel. The gel of claim 9 wherein the quantity of water is from 75% to 95% by weight of the gel.

11. A clear adhesive gel comprising 70% to 93% of water; 5% to 25% of partially hydrolysed polyvinyl alcohol; 0.5% to 1.5% of xanthan gum; 0.5% to 3% of a water-soluble plasticiser for the polyvinyl alcohol; and 0.05% to 0.35% of a water-soluble defoamer.

12. The gel of claim 11 wherein the plasticiser is an alkanol having from 2 to carbon atoms and from 2 to 3 hydroxy groups.

13. The gel of claims 11 or claim 12 wherein the defoamer is a monofunctional polyalkoxylated polyether.

14. The gel of any one of claims 11 to 13 wherein the gel can be laundered out of clothing in hot or cold water after it has dried. i: [N;\LIBZi255929D1:SAK:VMJ An article of manufacture comprising: a flexible dispenser wherein the dispenser has a dispensing opening of from about 7.1 to 77.5mm 2 contains a clear adhesive gel which can be dispensed therefrom by finger-pressure to form a glue line which does not run when extruded on paper in a vertical position; and said adhesive gel consisting essentially of a major quantity of water; partially hydrolysed polyvinyl alcohol in an amount sufficient to form fibre tearing bonds on paper upon hardening; a water-soluble thickening agent polymer compatible with the polyvinyl alcohol and in an amount sufficient to provide the adhesive gel with a thixotropic index and viscosity which permit extrusion of the adhesive from said opening in a steady stream by use of finger-pressure to form a horizontal glue line which does not run when placed on paper in a vertical plane; a water- soluble plasticiser which is compatible with the polyvinyl alcohol in an amount sufficient to plasticise the polyvinyl alcohol; and a water-soluble defoamer in an amount sufficient to prevent entrapped air from destroying the clarity of the gel.

16. The article of claim 15 wherein the dispenser has a dispensing opening of from 1.5 to 3mm in diameter.

17. The article of claim 15 or claim 16 wherein the portion of the dispenser with the gel contained therein is transparent. .18. The article of any one of claims 15 to 17 wherein said gel comprises 75% to 93% water; 5% to 20% of polyvinyl alcohol; 0.5% to 1.5% of the thickening agent; to 3% of the plasticiser; and 0.05% to 0.35% of the defoamer.

19. The article of any one of claims 15 to 18 wherein the thickening agent in said gel is sodium carboxymethylcellulose, sodium alginate or xanthan gum. The article of any one of claims 15 to 19 wherein the plasticiser in said gel is propylene glycol, glycerol, ethylene glycol, or diethylene glycol. 25 21. The article of any one of claims 15 to 20 wherein the gel has a wet tack of at least 35g.cm- 2

22. The article of any one of claims 15 to 21 wherein the gel has a time of set of 16 to 35 seconds at 25 0 C and a relative humidity of

23. The article of any one of claims 15 to 22 wherein the gel can be laundered out of clothing in hot or cold water after it has dried.

24. A flexible dispenser containing a clear adhesive gel substantially as hereinbefore described with reference to the accompanying drawings. A clear, thixotropic adhesive gel substantially as hereinbefore described with reference to any one of Examples 1 to 6. Dated 20 May, 1997 Borden Inc. Patent Attorneys for the Applicant/Nominated Person 3 SPRUSON FERGUSON IN:\LIBZI255929D :SAK:VMJ Thixotropic Wood Adhesive Gel Abstract A water based thixotropic adhesive gel is disclosed which comprises; an aqueous emulsion of polyvinyl acetate in an amount sufficient to form adhesive bonds on wood; partially hydrolysed polyvinyl alcohol in an amount sufficient to provide wet tack of the adhesive; glyoxal in an amount sufficient to provide water resistance to the adhesive; and wood flour in an amount sufficient to increase the water resistance imparted by the glyoxal and to provide sanding and staining properties to the adhesive; and xanthan gum in an amount sufficient to provide a thixotropic index and viscosity allowing extrusion of the gel lo from a flexible dispenser having a dispensing opening of about 1.85mm in diameter by applying finger-pressure to the dispenser while, upon extrusion, the gel forms a bead which does not run when applied in a horizontal line on wood in a vertical plane. A further water based thixotropic adhesive gel is disclosed which comprises water; partially hydrolysed polyvinyl alcohol, or wherein a portion of the polyvinyl alcohol is replaced with polyvinylpyrrolidone; a water-soluble high viscosity thickening agent polymer which is compatible with the polyvinyl alcohol and which imparts thixotropic properties to the gel; a water-soluble plasticiser for the polyvinyl alcohol; and a water- soluble defoamer in proportion of ingredients so that the viscosity of the adhesive will break down when a flexible tube or squeeze bottle dispenser is finger-pressed and have a sufficiently low viscosity to allow for easy extrusion from an orifice having a diameter of about 1.5 to 3.8mm. When pressure is released, after the desired amount of adhesive has flown out of the dispenser, the adhesive quickly reverts to very close to its original gel state so that it will not run on a vertical surface on porous and semiporous surfaces such as paper. An article of manufacture is also provided whereby the adhesive gel containing the 25 above ingredients is in a flexible dispenser from which the adhesive can be dispensed by finger-pressure. A conventional, flexible plastic, lw density, polyethylene tube dispenser (10) has a clear hollow tube portion (12) which has a capacity of about 90mL and a crimped, closed end The wall thickness of the polyethylene is 0.5mm. The closed end beyond crimp (14) has an extending flap (16) which has a cut out portion (18) so that the dispenser can be hung up and displayed or stored. The dispensing end (20) of tube (12) has a conventional screw threaded dispenser closure cap (22) which can effect opening and closing of orifice (26) by holding cap (22) in place while twisting cap end Dispenser contains adhesive gel (40) of this invention and the adhesive (40) in contact with tube (12) provide a clear appearance when the dispenser is viewed. II-I, I