JPH06234962A - Thixotropic wood adhesive gel - Google Patents

Abstract

PURPOSE: To obtain an aq. emulsion of a wood adhesive gel which can be easily dispensed by incorporating polyvinyl acetate, polyvinyl alcohol, glyoxal, wood flour, and xanthan gum in a specified ratio.

CONSTITUTION: Polyvinyl acetate (A) in an amt. sufficient to form adhesive bonds on wood, polyvinyl alcohol (B) in an amt. sufficient to provide wet tack of the adhesive, glyoxal (C) in an amt. sufficient to provide water resistance to the adhesive, wood flour (D) in an amt. sufficient to improve the water resistance imparted by the component (C), and xanthan gum (E) in an amt. sufficient to impart thixotropic properties and a viscosity under low shear stress of about 15,000 to 350,000 cP to the adhesive are mixed in water to prepare an aq. emulsion of an adhesive gel which has such a thixotropic index that allows extrusion of the gel from a flexible dispenser having a dispensing opening of about 0.073 in. in diameter by applying finger-pressure to the dispenser.

COPYRIGHT: (C)1994,JPO

Description

Detailed Description of the Invention

[0001]

[Industrial field of application] This application is filed on November 16, 1992.
No. 07 / 976,553, which is a continuation-in-part of our continuation application Ser.

The present invention relates to a thixotropic, water-based, general purpose, polyvinyl acetate adhesive gel for wood.

[0003]

A wide variety of general purpose, wood adhesives are used. However, such an adhesive has various drawbacks such as (a) overflow when placed on a vertical surface, and (a) it is difficult to perform conventional wood coloring in a dried adhesive, and (b) ) It has the drawback of being difficult to sand, or (c) difficult to waterproof.

The present invention is a conventional handheld plastic squeeze bottle for bonding wood.
It provides a thixotropic adhesive gel that can be easily dispensed from squeeze bottles. After being dispensed from the squeeze bottle, the adhesive does not flow on a vertical surface and can be sanded or colored,
A dry adhesive layer having waterproofness is formed.

The adhesive of the present invention comprises polyvinyl acetate as the main adhesive; xanthan gum as the thixotropic thickener; polyvinyl alcohol as the tackifier; and wood as the water resistant agent for the dried adhesive. Including a combination of flour and glyoxal,
Preferably, they consist essentially of them. Even more conventional components used in adhesive compositions, such as defoamers, preservatives and the like, can be used, as long as such components or amounts thereof do not adversely affect the adhesive.

Water-based polyvinyl acetate emulsions are familiar wood adhesives. I. Skeist
Edited by The Handbook of Adhesives, Third
The pages 388-390 of the Edition describe the use of polyvinyl alcohol as a protective colloid for imparting wet tack and as polyvinyl acetate emulsions, and pages 394-395 describe various substances of polyvinyl acetate. And thixotropy, pseudoplasticity and thickening are discussed, and page 398 describes the use of foam control agents and biocides in such adhesives.

1969 5 to P. Columbus et al.
U.S. Pat. No. 3,442,845, issued June 6, relates to polyvinyl acetate adhesives which, when dried, can be redispersed in cold or hot water. The adhesive composition of the 845 patent uses polyvinyl alcohol, a water-soluble gum, and cellulose ether as an anti-fusion aid for polyvinyl acetate. Polypropylene glycol and other polyhydroxy compounds are
It is described as a plasticizer for polyvinyl alcohol.

February 17, 1981 to P. Columbus
U.S. Pat.No. 4,251,400 granted to Sun is also redispersible in hot and cold water in the form of a dry film,
The present invention relates to a polyvinyl acetate adhesive which uses polyvinylpyrrolidone and a non-volatile water-soluble plasticizer as a fusion preventing aid. In addition to polyvinyl acetate and polyvinyl pyrrolidone, the patent also describes the use of polyvinyl alcohol, propylene glycol and water soluble ethers in adhesive compositions.

Lockti published January 28, 1987
European Patent Application Publication No. 0210052 to te provides a reactive adhesive, eg, cyanoacrylate, one at a time.
Or it relates to various tubes for dispensing at a rate of 2 drops. This patent describes an elastic plastic tube dispenser and, broadly, states that the adhesive may be thixotropic.

Technical Bulletin DB-15 entitled "KELZAN Xanthan Gum" by Merck & Co. describes xanthan gum as a thickener and a suspending agent for water-based systems, Its suspension, pseudoplasticity (thixotropic properties) and stability are enhanced.

Kelco's KELC, a division of Merck & Co.
O XANTHAN GUM, Third Edition is the above KELZAN BULLETI
It shows as many as N and also states that the xanthan gum provides a smooth flow under shear stress in adhesive formulations, which allows for the application of high solids. .

US Pat. No. 3,676,174: A mixture of wood flour and calcined gypsum is used to form a colorable substrate for molded articles. This patent discloses a composition of 1 part calcined gypsum; 1 part wood flour; 6 parts fine metal powder in step 5 of the second column. This dry powder is mixed with an equal amount of polyvinyl acetate diluted with water and used as a paint for clay objects.

US Pat. No. 2,510,257: Discloses an aqueous polyvinyl acetate emulsion containing glyoxal and polyvinyl alcohol. Glyoxal imparts water resistance to the adhesive.

US Pat. No. 4,638,022: pecan shell
shell) powder, using polyvinyl acetate,
Provided is a paint for wood or plastic which allows conventional wood coloring. The composition of this reference appears to be organic solvent based.

”Glue Gap 202 GF F of Garott Wade Company, Inc. located at 161 Sixth Avenue, New York, NY
A commercial product referred to as "iling" is an aqueous polyvinyl acetate emulsion adhesive containing wood fiber or wood flour. This product is viscous but not at all or at all thixotropic and also wood fiber. A lot of
Shaking is necessary to settle easily and disperse the wood fibers.

[0016]

SUMMARY OF THE INVENTION A thixotropic, water-based polyvinyl acetate containing polyvinyl alcohol, xanthan gum, wood flour and glyoxal is provided.

[0017]

Wood flour and glyoxal act synergistically to provide a higher level of water resistance as compared to a similar composition containing no wood flour but the same level of glyoxal. To the dried adhesive. Due to its thixotropic nature, the viscosity of the adhesive breaks when a flexible tube or squeeze bottle is acupressured, easily and steadily and continuously in small orifices, e.g. 0.15 inch orifice, or about 1/16 inch wide and 5 /
Typical rectangular glue applicat with 16 inch length
or slit) and has a sufficiently low viscosity that it can be extruded. When the pressure is released after the desired amount of adhesive has flowed out of the orifice, the adhesive quickly recovers very close to its original gel state, allowing it to be applied to a porous support such as a vertical wood surface. When applied, the horizon of the gel does not flow.
The adhesive has good wet tack and a cure rate sufficient to allow repositioning of the two wood supports during the drying of the adhesive between the two wood supports.

Further aspects of the invention can be clearly read from the entire description and claims.

The adhesive of the present invention comprises a polyvinyl acetate in an amount sufficient to provide an adhesive bond upon drying; an amount of polyvinyl alcohol sufficient to increase the wet tack of the adhesive; A sufficient amount of glyoxal to impart; an amount of wood flour that acts synergistically with glyoxal to increase the water resistance imparted by glyoxal; and as measured by an RVF Brookfield viscometer using a number 6 spindle ,
Aqueous dispersion containing sufficient amount of xanthan gum to give a thixotropic index of about 1.5 to 7 when divided by the viscosity of the gel at 25 RPM at 2 RPM divided by the viscosity at 20 RPM (rev / min). And is also referred to herein as an emulsion. Wood flour also allows sanding and staining of dried adhesives.

The gel of the present invention has good wet tack. It has, for example, an adhesive bond that tears wood fibers.
Allowing sufficient time to position the second piece of wood by sliding the surface of the second piece of wood against the first piece of wood before it occurs between the two supports,
It has a sufficiently slow cure rate to allow the two pieces to be permanently positioned in that position.

Water, polyvinyl acetate, polyvinyl alcohol, xanthan gum, glyoxal and wood flour generally make up at least 90%, preferably 95%, particularly preferably 98% of the adhesive composition.

Xanthan Gum Xanthan gum is a natural, high molecular weight, branched polysaccharide. It functions as a hydrophilic colloid that thickens, suspends and stabilizes water-based systems. The amount of xanthan gum used in the present invention is an amount sufficient to impart the desired thixotropic index and viscosity to the adhesive gel. Such amount can vary over a wide range, for example in the range of about 0.1% to 1.5% by weight of the adhesive, preferably the amount of xanthan gum is about 0. It can be varied in the range of 2% by weight to 0.8% by weight.

Other water-soluble thickeners have also been tried for use in the present invention, but are unsatisfactory due to their immiscibility and lack of adequate stability, as they do not resist the water resistance of dried adhesives. Adversely affect. Other thickeners which have proven to be unsuitable include hydroxyethyl cellulose; alginates; sodium salt of carboxymethyl cellulose (CMC); and polyvinylpyrrolidone. The superiority of xanthan gum over other hydrophilic gums, such as CMC, was unpredictable. CMC is the preferred hydrophilic gum when used as the gel thickener in the parent case of the present application. However, the parent case gel does not contain dispersed polyvinyl acetate, glyoxal or wood flour, and if desired only xanthan gum as a thickening agent.

The term "thixotopic" as used herein is also meant to cover pseudoplasticity. The thixotopic index used in the present invention allows the extrusion of gels through small dispensing openings of flexible dispensers, eg tubes or squeeze bottles, using acupressure. Due to thixotropy, the adhesive recovers to a high viscosity quickly after extrusion from the orifice if no force or shear stress is applied. The adhesive gel does not flow when applied to a vertical wood surface after being extruded through the small orifice of the dispenser used in the present invention. By not flowing, the adhesive remains completely at the location of the area where it is extruded with minimal application unless external force is applied. The minimum coating amount is a small amount of downward creep due to gravity, for example, 0.1.
Includes downward creep of less than 5 inches, preferably less than 0.1 inch. The use of small orifices in the dispenser, eg, orifices less than 0.1 inch in diameter, eg, orifices less than 0.73 inch in diameter, minimizes creep.

The thixotropic index for the adhesive gels according to the invention can be varied in the range from about 1.5 to 7, preferably from about 2 to 5, particularly preferably from 2.5 to 4.0. As used herein, the term "thixotropic index" refers to the read viscosity centipoise at 2 RPM of the gel at 25 ° C. using a number 6 spindle and using an RVF Brookfield viscometer. Is the value obtained by dividing the read viscosity at 20 RPM by the centipoise.

Viscosity readings in the present invention are taken after the gel has been allowed to rest undisturbed for a period of time, eg 12 hours. The adhesive gel of the present invention is stable.

In order to prevent the settling of wood flour in the adhesive and to prevent its flow after it has been extruded from the squeeze bottle, the adhesive of the present invention may be used at rest or under low shear stress.
It has a high viscosity. However, because of its thixotopic nature, it can be poured through the opening of the container or at a lower level when the container is tilted. This facilitates drainage of the adhesive from a plastic bottle glue dispenser with a small opening. On the other hand, at the viscosity used in the present invention, a non-thixotopic adhesive or an adhesive with little thixotropy is
It can be difficult to remove from a plastic bottle with a small orifice, and in particular it can be difficult to remove substantially all of the adhesive.

The adhesive gel of the present invention is 2 RPM (rotation number /
Min), RV using number 6 spindle
Viscosity at 25 ° C measured by F Brookfield viscometer is about 15,000 cps (centipoise) to 350,
000 cps, preferably a viscosity at 25 ° C of about 40,
It has 000 cps to 120,000 cps. When using a No. 6 spindle and measuring at 20 RPM with an RVF Brookfield viscometer at 25 ° C,
As long as the thixotopic index is within the ranges described herein, the viscosity is about 10,000 cps to 50,000 cps, preferably about 14,000 cps to 35,000 c.
ps.

Polyvinyl Acetate The adhesive used in the present invention is predominantly polyvinyl acetate, although polyvinyl alcohol also forms an adhesive bond.

The polyvinyl acetate can have a molecular weight as is conventional in polyvinyl acetate wood adhesives, for example about 30,000 to 200,000. Preferably, the polyvinyl acetate has a molecular weight of about 30,000 to 100,000, although higher or lower molecular weight resins can be used. It is preferred to use the polyvinyl acetate emulsion, which is a homopolymer dispersion (emulsion) having a total solids content of about 40% to 65%, based on the weight of the polyvinyl acetate emulsion.

Polyvinyl Alcohol As used throughout this specification and claims, the term "polyvinyl alcohol" refers to fully hydrolyzed polyvinyl alcohol and partially hydrolyzed polyvinyl alcohol, such as in polyvinyl acetate aqueous emulsions. It is intended to include those useful as emulsifiers.

The polyvinyl alcohol is preferably partially hydrolyzed to have a molecular weight of about 25,000-100,000.
0, preferably about 40,000-80,000. The viscosity of polyvinyl alcohol ranges from a wide range, for example, about 5 or 6 cps, to what is referred to as low viscosity in the art to 60% RPM at 20 ° C. for 4% aqueous solution.
It can be varied over a wide range up to what is referred to in the art as high viscosity with a viscosity of 40-50 cps as measured by an RVF Brookfield viscometer using a number 1 spindle at. The preferred degree of hydrolysis for partially hydrolyzed polyvinyl alcohol is about 87% to 89%.
Is. The partially hydrolyzed polyvinyl alcohol is
Preferred for consumer products as opposed to industrial applications. The reason for this is that the use of fully hydrolyzed polyvinyl alcohol confers to the composition, in general, a low stability, e.g. lacking freeze-thaw stability or leaving it for a relatively short time to allow it to release. It shows liquid phenomenon.

The amount of polyvinyl alcohol in the gel is that amount which increases the wet tack of the adhesive. This is, for example, from about 1.5% to 15% by weight of the adhesive over a wide range.
It can be varied in the range of% by weight, preferably in the range of about 2.5% to 7% by weight of the adhesive. For polyvinyl acetate emulsion,
A small amount of partially hydrolyzed polyvinyl alcohol is often used as the protective colloid. The total amount of polyvinyl alcohol in the adhesive of the invention is the amount used as protective colloid in the polyvinyl acetate emulsion,
For example, additional amounts such as amounts to increase the wet tack of the adhesive.

Glyoxal Glyoxal acts synergistically with wood flour to impart water resistance to the dried adhesive. The amount of glyoxal used in the present invention is an amount sufficient to impart water resistance to the dried adhesive. Glyoxal is about 0.00 of adhesive
A minute amount of about 5% by weight is sufficient. The amount of glyoxal can generally vary from about 0.005% to 0.4% by weight of the adhesive, preferably about 0.01% to 0.2% by weight of the adhesive. Range, and particularly preferably about 0.02% to 0.1% by weight of the adhesive.
Is. Glyoxal can be used even more than this, but large amounts adversely affect stability, eg freeze-thaw stability, and upon aging tend to result in excessive thickening of the composition. Glyoxal is generally added to the adhesive in an aqueous solution, eg 20% to 5% of glyoxal.
It is formulated in the form of a 0% aqueous solution.

Plasticizers If desired, water-soluble plasticizers for polyvinyl alcohol can also be used in the composition. Such a plasticizer softens the polyvinyl alcohol and makes the polyvinyl alcohol even softer. Examples of such plasticizers include alkanes having 2-5 carbon atoms and 2-3 hydroxyl groups, such as polypropylene glycol; glycerol; ethylene glycol; and diethylene glycol. However, ethylene glycol and diethylene glycol are somewhat toxic. The amount of water-soluble plasticizer is an amount sufficient to plasticize the polyvinyl alcohol, and can generally vary from about 0.5% to 3% by weight of the adhesive gel. Although such plasticizers can be used, it is desirable not to use them if high water resistance is desired.

Water-insoluble plasticizers for polyvinyl alcohol can also be used in the adhesives of this invention. Examples of such plasticizers include butylbenzyl phthalate; dibutyl phthalate; tricresyl phosphate and the like. If used, the amount of water insoluble plasticizer is generally less than 1% by weight of the adhesive, eg about 0.1.
% By weight to 0.5% by weight.

Wood Flour Wood flour can easily pass through the 0.073 inch diameter orifice in the composition of the present invention after incorporation and suspension in the adhesive. The wood flour remains suspended in the gel for extended periods of time, for example at least one month, without significant settling, and does not prevent the smooth discharge of the gel from the dispenser orifice. Wood flour is generally fine particles with a particle size (US Standard Sieve Series) of less than about 10 mesh (2,000 microns), preferably less than 20 mesh (850 microns). Such wood flour may be hardwood, such as maple, or softwood, such as soft pine. A preferred wood flour is coniferous wood flour.

The total amount of water water, when formulating the adhesive polyvinyl acetate as polyvinyl acetate emulsion aqueous are those including the water from the polyvinyl acetate to be used in making the adhesive. The total amount of water includes the amount of water added during the production of the adhesive and the amount of water carried in by the constituents. The amount of water can generally vary from about 40% to 85% by weight of the adhesive, preferably 45% to 7% by weight of the adhesive.
5% by weight, particularly preferably 50% to 65% by weight of the adhesive
It can be varied within the range of weight%.

Water-Soluble Defoamers Conventional water-soluble defoamers are generally used in the adhesives of this invention. Such defoamers include silane defoamers and polyalkoxylated polyethers,
For example, butoxyoxyethylene-propoxyl propylene glycol may be mentioned. The amount of defoamer is an amount that maintains the density of the gel, prevents excessive foaming during the manufacturing process, and facilitates gel filling of the dispenser. Generally, the amount of defoamer can vary from about 0.05% to 0.35% by weight of the gel composition.

The dispenser for dispenser thixotropic adhesive gel, flexible, low density polyethylene squeeze bottle conventionally example, may be one volume 4 fluid ounce (fluid ounces). For example, ELMER'S SCHOOL GLUE of B
A four fluid ounce plastic squeeze bottle used for orden, Inc. is suitable. Such dispensers are shown in the above-referenced continuing patent application, which is hereby incorporated by reference in its entirety. To dispense the gel from the dispenser squeeze bottle onto a support, such as wood, use finger pressure between the thumb and the remaining four fingers, or between the thumb and the other fingers. The orifice of the dispenser cap has a diameter of about 0.06-0.15 inch, preferably 0.07-.
0.10 inch, particularly preferably about 0.07-0.
Has 08 inches. Approximately 1/16 inch wide and 5/16 inch as found in many wood adhesive dispensers
The use of rectangular slits with inch lengths is also suitable. The thixotropic gel adhesive, despite its high viscosity in the unhindered state, due to its thixotropic nature, flows out of the cap orifice in a steady state flow when acupressured. The area of the opening of such a dispenser is from about 0.011 to about 0.12 square inches.

A preferred method for producing the adhesive gel of the present invention is as follows. Add water to the tank with the mixer and start the mixer. Disperse the polyvinyl alcohol and xanthan gum in the mixture. Then,
Add defoamer and allow polyvinyl alcohol to "wet
t) ”and continue mixing until softened. Continue mixing and raise temperature to 85 ° C.-90 ° C. to obtain a smooth, homogeneous mixture.
When cooled to about 3%, the emulsion is polyvinyl alcohol.
Containing about 50% of polyvinyl acetate emulsified with
Add the polyvinyl acetate emulsion so that the balance is water. Mixing is continued, the temperature is reduced to about 50 ° C., then glyoxal, wood flour and any preservatives are added. Continue mixing until the mixture is smooth and homogeneous.

The following examples are provided so that those skilled in the art may more fully understand the invention described herein. All parts and percentages in the examples and other parts of this application are parts by weight and percentages by weight, unless otherwise noted. Unless otherwise specified, the viscosity measurement as used herein uses an RVF Brookfield viscometer having a spindle number 6 at 25 ° C.
The term "Low Shear" refers to viscosity measurements at 2 RPM (revolutions per minute), while "High Shear (Hi Shear)
The term "gh Shear)" refers to viscosity measurements made at 20 RPM.

[0043]

EXAMPLES Example 1 This example demonstrates the composition and properties of the adhesive gels of the present invention.

[0044] 1 partially hydrolyzed polyvinyl alcohol 2 American Wood Fibers, Inc. Pine wood flour N
o. 14020 3 Dispersible grade xanthan gum marketed by Merck & Co 4 Monofunctional polyalkoxylates supplied by the Thomas W. Dunn Corp of Ridgefield, N. J as a 40% aqueous solution of 4 glyoxal. Polyether Acetate Defoamer Plasticizer for Polyvinyl Acetate Marketed by Vesical Chemical Corp. of DEFOAMER 622 6 Chicago I11 The adhesive of Example 1 had an orifice of about 0.073 inch diameter. Easily dispensed by finger pressure from an elastic plastic 4 ounce polyethylene bottle with a closed cap. After dispensing on a piece of pine wood held vertically, it forms a uniform, thin, horizontal bead that does not flow, and when dried, a wood fiber tear adhesive bond between two pieces of wood Was formed. The gel can be dispensed in steady state flow through the dispenser orifice. It has a thixotropic index of about 3.5 after about 24 hours of manufacture and has a viscosity of 11 at a spindle speed of 2 RPM when measured at 25 ° C. with an RVF Brookfield viscometer using a No. 6 spindle.
Viscosity 32 at 5,000 cps, 20 RPM spindle speed,
It has 500 cps. Then, using the same method and apparatus, the viscosity measurement was performed as follows. After standing for about 2 days, the viscosity at 2 RPM is 117,500 cps, and 2
Viscosity at 0 RPM is 33,000 cps; after 3 days of manufacture, viscosity at 2 RPM is 135,000 cps, 20
The viscosity at RPM was 34,500 cps.

Example 2 This example provides another formulation with the superior properties of the present invention.

[0046] 1 Merck & Co. product 2 Diluted in water 3 American Wood Fibers, Inc. Pine wood flour N
o. 14020 4 Rohm and Haas Microbicide 5 Rohm and Haas Company Microbicide 6 Rhone-Poulanc Defoamer Product As in Example 1, the adhesive was a plastic dispenser bottle diameter 0.073 inches. It was easily dispensed from the orifice and when dispensed on a vertical surface, the bead of adhesive did not flow. After manufacture, the adhesive had a viscosity of 8 at 2 RPM at 2 RPM spindle speed at 25 ° C.
It had a viscosity of 22,000-26,000 cps at 20 RPM spindle speed at 25 ° C. for a thixotropic index of 3.5. Two days after production, the viscosity at 2 RPM was 89,
000 cps and a viscosity of 24,000 cps at 20 RPM for a thixotropic index of 3.3.
Two weeks after production, the viscosity at 2 RPM is 85,000.
0 cps, viscosity at 20 RPM is 25,000 cp
It was s. All viscosity measurements were made using a RVF Brookfield viscometer with a number 6 spindle at 25 ° C.

Example 3 As a thickener, 1.20% of hydroxyethyl cellulose was used.
Was used and about 0.7% less water was used to balance the additional hydroxyethyl cellulose,
An adhesive gel having the same composition as in Example 1 was prepared. Hydroxyethyl cellulose is not compatible with the product as it aggregates unevenly throughout the mixture, leaving the water content of the mixture, and quickly separating from the mixture.

Example 4 An adhesive gel having the same composition as in Example 1 was prepared except that 1.65% of polyvinylpyrrolidone and 0.60% of carboxymethyl cellulose were used as thickeners. Again, less than a balanced amount of water was used to increase the amount of thickener. The viscosity of the gel showed an immediate decrease and was not suitable for use in the present invention.

Example 5 0.6% of carboxymethyl cellulose (CMC) was used in place of 0.5% of xanthan gum, and the amount of water was adjusted to 0.
1% reduction to compensate for the reduced amount of thickener,
An adhesive gel having the same components as in Example 1 was prepared. This formulation was unsatisfactory due to the reduced viscosity. Therefore, the initial viscosity at 2 RPM was 145,000 cps and the initial viscosity at 10 RPM was 75,000 cps. 20R due to its high viscosity
Since the viscosity could not be read on the scale of the instrument at PM, a speed of 10 RPM was used as the high speed. 2 days after production, viscosity is 2RPM, 45,000
At 0 cps, at 20 RPM, it dropped to 27,000 cps. One week after the manufacturing date, the viscosity is 2RPM and 25,000cps
And was 175,000 at 20 RPM. Two weeks after manufacture, the viscosity was 15,000 cps at 2 RPM and 20,500 cps at 20 RPM. Viscosity measurements were made as in Example 2. It can be seen that both viscosity and thixotropic index decrease rapidly when CMC is used as the thixotropic agent.

Example 6 This example demonstrates the synergistic effect of glyoxal and wood flour to achieve the water resistance of the dry adhesive gel of the present invention.

In this example, four adhesive gel samples were used. Sample 4 was the adhesive gel of Example 2 above. The composition of Sample 1 was the same as that of Example 2 except that it contained neither glyoxal nor wood flour, and there were no other differences in the formulation. The composition of Sample 2 is the same as that of Example 2 except that it does not contain wood flour,
There were no other differences in the formulation. The composition of Sample 3 is that of Example 2 except that it does not contain glyoxal.
The composition was the same and there were no other differences in the formulation. Each sample is No. 34 wire wrap rod (wi
It was pulled down with a re wrap rod) and made into a band about 2 inches wide of an adhesive film on a glass plate. The withdrawn adhesive was allowed to dry by standing for 6 days at 75 ° F and 50% relative humidity, then tested as follows.

Two series of tests were performed. In the first series, one drop of deionized water was placed on each drawdown adhesive and the time taken to whiten (slightly turn white) each film was measured. A film that takes a long time to change its color is a film having high water resistance. Immediately after observing discoloration, the area of the film under the drop of water was rubbed with a finger. The easy dispersion of the film under the drops of water indicates poor water resistance, while the poor dispersibility of the affected areas under the drops of water makes it more resistant to water. Indicates good. In this series of tests,
The time for the film to whiten is 2 seconds for Sample 1;
9 seconds for sample 2; 3 for sample 3
Seconds; and for sample 4, it was 35 seconds. In this series of tests, the friction of the film area under the drop of water was shown to disperse easily for Sample 1;
Sample 2 is shown to disperse somewhat; Sample 3 is shown to disperse easily;
Sample 4 showed no dispersion.

In a second series of tests, a drop of water was placed on each of the samples until the area under the water became opaque (opaque white or off-white). The film area under the drop of water became opaque in 1 minute for sample 1 and the film dispersed easily in water when rubbed with a finger; for sample 2, opaque in 2 minutes and rubbed with a finger. Some dispersion of the film was then seen; for sample 3 it became opaque in 1 minute and the film disperses easily when rubbed with a finger and for sample 4 45-45.
It became opaque at 60 minutes, did not disperse when rubbed with a finger, and instead peeled off into large fragments.

The water droplets of sample 4 in both series of tests were:
"Beading" not found in other samples
Was also observed. Beading refers to a hydrophobic surface as opposed to a hydrophilic surface.

From Example 6, glyoxal and wood flour in the composition of the present invention act synergistically to increase water resistance in the dried adhesive.

Example 7 This example can provide another formulation having the superior properties of the present invention.

[0057] Example 8 This example can provide another formulation with the superior properties of the present invention.

[0058]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yojesh by Babbhai Patel Ashford Glenn Drive, Gahanna, Ohio, USA 802

Claims (25)

[Claims] 1. (A) An amount of polyvinyl acetate sufficient to impart an adhesive bond to wood; (B) An amount of polyvinyl alcohol sufficient to impart wet tack to the adhesive; (C) Water resistant to the adhesive. A sufficient amount of glyoxal to impart water resistance; (D) an amount of wood flour sufficient to improve the water resistance imparted by the glyoxal; and (E) a thixotropic property of the adhesive and a low shear stress. Viscosity at about 15,000 cps to 350,000 cps
And xanthane gum in an amount sufficient to provide the gel with the thixotropic properties of extruding the gel from a flexible dispenser having a dispensing opening of about 0.073 inches in diameter by applying finger pressure to the dispenser. An aqueous emulsion of a thixotropic adhesive gel. 2. The amount of thickener is measured with an RVF Brookfield viscometer using a number 6 spindle,
An amount sufficient to give a thixotropic index of about 1.5 to 7 when the viscosity of the gel at 2 RPM at 25 ° C. is divided by the viscosity of the gel at 20 RPM.
The amount of polyvinyl alcohol is at least 1.5% by weight of the gel, and upon extrusion through the dispensing opening, the gel does not flow when applied horizontally to a vertical wood surface, leaving beads. The gel according to claim 1, which is formed. 3. The thixotropic index is about 2 to
The gel of claim 2, which is 5.0 and the amount of wood flour is sufficient to impart color and sanding properties to the dried adhesive. 4. About 10% by weight polyvinyl acetate.
~ 45%; Water about 40-85%; Polyvinyl alcohol about 1.5% -15%; Xanthan gum about 0.1%-
1.5%; glyoxal about 0.0005% to 0.4
%; And wood flour from about 2% to 20%. 5. A water-soluble defoaming agent from about 0.05% by weight to about 0.
The gel according to claim 1, containing 3% by weight. 6. The gel according to claim 4, wherein the amount of water is about 45% to 75% by weight and the polyvinyl acetate is 20% to 40% by weight. 7. By weight, (A) about 45% to 75% water; (B) about 20% to 40% polyvinyl acetate; (C) about 2.5% to 7% polyvinyl alcohol; (D) about xanthan gum. The gel according to claim 1, comprising: (E) about 0.01% to 0.2% of glyoxal; and (F) about 3% to 15% of wood flour. 8. At least 95% by weight of the gel is
The gel according to claim 7, which is composed of water, polyvinyl acetate, partially hydrolyzed polyvinyl alcohol, xanthan gum, glyoxal and wood flour. 9. By weight, (A) about 40% to 85% water; (B) about 10% to 45% polyvinyl acetate; (C) about 1.5% to 15% polyvinyl alcohol; (D) about xanthan gum. 0.1% to 1.5%; (E) Glyoxal about 0.005% to 0.4%;
And (F) an aqueous adhesive gel emulsion containing about 2% to 20% wood flour. 10. The gel according to claim 9, which is thixotropic and has a viscosity at low shear stress of 15,000 cps to 350,000 cps. 11. The gel of claim 10 having a thixotropic index of about 1.5-7. 12. Water about 45% to 75%; Polyvinyl acetate about 20% to 40%; Polyvinyl alcohol about 2.5% to 7%; Xanthan gum about 0.2% to 0.8.
%; Glyoxal from about 0.02% to 0.1%; and wood flour from about 4% to 8%. 13. A gel according to claim 12, at least 98% of which is composed of water; polyvinyl acetate; polyvinyl alcohol; glyoxal; wood flour; and xanthan gum. 14. A polyvinyl alcohol in an amount sufficient to impart wet tack to the adhesive, about 0.005% to 0.4% glyoxal, about 2% to 20% wood flour, and thixotropic to the gel. Sufficient amount of xanthan gum to provide the desired properties and the viscosity at which the wood flour is suspended and the gel can be discharged by applying finger pressure to a flexible plastic bottle having an orifice of 0.073 inch diameter. A thixotropic aqueous polyvinylacetate emulsion adhesive gel, containing and wherein each said amount is by weight for the gel. 15. The amount of polyvinyl alcohol is 1.5.
The gel according to claim 14, which is between 15% and 15%. 16. The amount of glyoxal is about 0.01%.
.About.0.2%, the amount of wood flour is about 3% to 15%, and the amount of xanthan gum is 0.1% to 1.5.
% Of the gel according to claim 15. 17. The gel according to claim 16, wherein the wood flour is soft pine wood wood flour. 18. The amount of polyvinyl alcohol is about 2.
The gel according to claim 17, which is 5% to 7%. 19. By weight, (A) about 40% to 85% water; (B) about 10% to 45% polyvinyl acetate; (C) about 1.5% to 15% polyvinyl alcohol; (D) about xanthan gum. 0.1% to 1.5%; (E) Glyoxal about 0.005% to 0.4%;
And (F) Wood powder of about 2% to 20% is mixed, a thixotropic index of about 1.5 to 7, a low shear stress viscosity of about 15,000 cps to 350,000 cps, and a high shear stress viscosity of about 10,000 cps. A method for making an aqueous emulsion of a thixotropic adhesive gel comprising forming a gel having ˜50,000 cps. 20. An adhesive gel produced by the method of claim 19. 21. (A) Water about 45% to 75%; (B) Polyvinyl acetate about 20% to 40%; (C) Polyvinyl alcohol about 2.5% to 7%; (D) Xanthan gum about 0.2. % -0.8%; (E) Glyoxal about 0.01% -0.2%; and (F) Wood flour about 3% -15% are mixed to give a thixotropic index of about 2-5 and low shear. Stress viscosity about 4
20. The method of claim 19, comprising forming the gel having a high shear stress viscosity of about 14,000 cps to 35,000 cps. 22. The method according to claim 19, wherein the polyvinyl alcohol is partially hydrolyzed. 23. By weight, (A) water 50% to 65%; (B) polyvinyl acetate 20% to 40%; (C) polyvinyl alcohol 2.5% to 7%; (D) xanthan gum about 0.2. 20. The method of claim 19, comprising: (E) about 0.02% to 0.1% glyoxal; and (F) about 3% to 15% wood flour. 24. The amount of wood flour is 4% to 8%,
24. The method of claim 23, wherein at least 95% of the mixture consists of water, polyvinyl acetate, polyvinyl alcohol, xanthan gum, glyoxal and wood flour. 25. The adhesive composition produced by the method of claim 23, wherein the dried adhesive is sandable and tintable.