JPH04261488A - Adhesive - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to adhesives, and more particularly to woodworking adhesives.

0002

[Prior Art] Vinyl ester (co)polymer emulsions, typified by polyvinyl acetate (co)polymer emulsions, are used as adhesives for woodworking, etc.
Water resistance and alkali resistance are poor, and there is a strong demand in the industry for improvement in these points. Many attempts have been made to solve this problem. For example, it has been proposed to add crosslinking agents such as metal salts, epoxy compounds, isocyanate compounds, and aziridine compounds to introduce crosslinking bonds into resins, but the reality is that this is not always at a fully satisfactory level. It is. This is thought to be because the resin itself is hydrophilic, so even if the crosslinking density is increased considerably, if it is immersed in water, it will absorb water, resulting in a significant decrease in the elastic modulus of the adhesive, leading to a decrease in adhesive strength. From this point of view, attempts have been made to copolymerize hydrophobic monomers in order to improve the water resistance of the resin itself. For example, Japanese Patent Publication No. 51-12653 proposes copolymerizing a specific amount of higher carboxylic acid vinyl ester having 5 to 12 carbon atoms. Similar copolymerization has also been proposed in JP-A-52-47833. All of these are proposals for pressure-sensitive adhesives. The present inventors also proposed blending an isocyanate compound etc. into the above-mentioned higher carboxylic acid vinyl ester copolymer emulsion and using it as a contact adhesive (Japanese Patent Publication No. 62-3
No. 1755, Special Publication No. 63-18634). However, these proposals were all for adhesives (pressure-sensitive adhesives) with a low elastic modulus, and could not be applied to woodworking adhesives that require a high elastic modulus.

0003

SUMMARY OF THE INVENTION The present invention provides means for improving the water resistance of the vinyl ester copolymer emulsion adhesive for woodworking.

0004

[Means for Solving the Problems] Among higher carboxylic acid vinyl esters, the present inventors focused on vinyl pivalate as a monomer that can increase the elastic modulus, and as a result of various studies,
It has been discovered that a vinyl ester copolymer emulsion containing a specific amount of vinyl pivalate, having a specific copolymerization composition, and having a specific Gas La transition temperature exhibits excellent water resistance. It has been discovered that an adhesive with excellent water resistance can be obtained by using That is, the present invention uses a copolymer emulsion that is a copolymer of vinyl pivalate and an ethylenically unsaturated monomer and has a glass transition temperature of -10°C or higher as a vinyl ester copolymer emulsion. According to
The present invention provides an adhesive composition with excellent water resistance. In the present invention, the ethylenically unsaturated monomer copolymerizable with vinyl pivalate is preferably one or more monomers selected from the group of ethylene, vinyl acetate, and acrylic ester. Examples of acrylic esters include methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate. The composition of these monomers in the copolymer of the present invention is not particularly limited as long as the copolymer has a glass transition temperature of -10°C or higher. The proportion of vinyl pivalate units is 5 to 90% by weight, preferably 10 to 80% by weight, and the proportion of vinyl acetate units is 5 to 80% by weight, preferably 10 to 80% by weight. Other copolymerized units include ethylene units of 50% by weight or less, preferably 5 to 50% by weight, more preferably 5 to 40% by weight,
The content of acrylic ester units is 50% by weight or less, preferably 5 to 50% by weight. If the vinyl pivalate unit content is less than 5% by weight, the water resistance will not be improved sufficiently, and if it exceeds 90% by weight, film forming properties will be poor even if the content of ethylene units or vinyl acrylate units is large, and it will not be used as an adhesive. It stops working. If the content of vinyl ester units other than vinyl pivalate units is less than 5% by weight, adhesion to polar substances will be impaired, and if it exceeds 80% by weight, water resistance will decrease. Ethylene units and acrylic acid ester units are also components for imparting hydrophobicity to vinyl ester resins, but they are also components for effectively internally plasticizing vinyl ester resins, for which film-forming properties are insufficient with vinyl ester resins alone. It is. Therefore, an ethylene unit and an acrylic acid ester unit may be used in combination, but it is sufficient if either one is included. When mainly using ethylene units, the content of ethylene units is 5
The amount is preferably 50% by weight or less, and if it is less than 5% by weight, the film-forming properties are insufficient, and if it exceeds 50% by weight, the cohesive force decreases, leading to a decrease in adhesive strength. When acrylic ester units are mainly used, the optimum amount of acrylic ester varies depending on the number of carbon atoms in the alkyl group, but is preferably approximately 5 to 50% by weight. If it is less than 5% by weight, the film forming property is not sufficient, and 50% by weight or less.
This is because if it exceeds % by weight, the cohesive force decreases, leading to a decrease in adhesive strength.

[0005] The composition of the copolymer in the present invention is based on the above-mentioned composition, but as long as the object of the present invention is not impaired,
A monomer copolymerizable with vinyl pivalate and vinyl acetate may be copolymerized. For example, acrylic acid, methacrylic acid,
Unsaturated carboxylic acids such as itaconic acid, maleic acid and fumaric acid, methacrylic acid esters such as methyl methacrylate and ethyl methacrylate, N-methylolacrylamide, vinyl acrylamide propionate, vinyl versatate (Veova-10, Shell (chemical trade name), vinyl chloride, etc. The copolymer emulsion used in the present invention is obtained by conventionally known emulsion copolymerization using a water-soluble initiator in the presence of a conventionally known surfactant and a protective colloid such as polyvinyl alcohol (PVA) or hydroxyethyl cellulose. In the adhesive of the present invention, necessary additives such as a plasticizer, a fungicide, an antifoaming agent, a thickener, and an inorganic pigment are added to the above-mentioned emulsion depending on the individual purpose. Furthermore, in order to further improve the level of water resistance obtained by the present invention, melamine resins, urea resins, epoxy compounds, isocyanate compounds, polyvalent metal salts, aziridine compounds, etc. can also be appropriately combined.

[0006]

[Examples] The present invention will be explained in more detail with reference to Examples below. In the examples, "parts" and "%" are based on weight unless otherwise specified.

Example 1 5 parts of partially saponified PVA with an average degree of polymerization of 1000 and a degree of saponification of 88 mol% was added to 85 parts of ion-exchanged water in a pressure-resistant autoclave equipped with a stirrer, a nitrogen inlet pipe, and various drug injection pumps.
6 parts of vinyl acetate and 10 parts of vinyl pivalate were added, the mixture was purged with nitrogen, the temperature was raised to 60°C, and ethylene was pressurized to 45 kg/cm 2 . Polymerization was started using a 1% hydrogen peroxide aqueous solution and a 5% Rongalite aqueous solution, and then 25 parts of vinyl acetate and 40 parts of vinyl pivalate were continuously added over 3 hours. The obtained copolymer emulsion had a solid content of 53.1% and a viscosity of 1,600 mPas·s.
(30°C), and the copolymer composition determined by NMR is vinyl pivalate: vinyl acetate: ethylene = 49:31:
20 (weight ratio). Further, the glass transition temperature (Tg) determined by DSC was -4°C. Next, an adhesion test was conducted using the above emulsion under the following conditions I and II. The results are shown in Table 1. (Adhesion test-I) (a) Test piece; Birch material (b) Adhesive composition; Emulsion alone (c) Coating amount;
Apply 125g/m2 on one side (d) Press: 15kg/
cm2, 24 hours (e) Adhesive force measurement conditions: Measured by compression shear method, normal condition; Measured immediately after preparing an adhesive test piece.・Hot water resistance: The test piece is immersed in 60°C warm water for 3 hours, then immersed in room temperature water until cooled, and subjected to the test while still wet. (Adhesion Test-II) (a) Test piece; Birch material (b) Adhesive composition;
A117 (weight 1700, saponification degree 98 mol%) 10
% aqueous solution, 10 parts of calcium carbonate, and 10 parts of polymethylene polyphenyl isocyanate ("Millionate MR100" manufactured by Nippon Polyurethane) were used. (c) Coating amount: 125 g/m2 applied on one side (d) Pressing: 15 kg/cm2, 24 hours (e) Adhesive force measurement conditions: Compression shear method.・Normal condition: Measure immediately after creating the adhesive test piece.・Repeated boiling: After immersing the test piece in boiling water for 4 hours,
The sample is dried in air at 0°C for 20 hours, then immersed in boiling water for 4 hours, then immersed in water at room temperature until cooled, and then subjected to the test while still wet.

Example 2 The autoclave used in Example 1 had an average degree of polymerization of 100.
0, 5 parts of partially saponified PVA with saponification degree of 88 mol% and 20 mol of polyoxyethylene added nonyl phenyl ether 2
After dissolving 1 part in 95 parts of ion-exchanged water, 39 parts of vinyl acetate,
Add 10% of a mixture of 31 parts of vinyl pivalate and 30 parts of butyl acrylate, and after purging with nitrogen, heat up to 70°C.
Polymerization was initiated using a 2% ammonium persulfate aqueous solution,
The remaining monomer mixture was then added continuously over a period of 3 hours. The obtained copolymer emulsion had a solid content of 54.0%,
Vinyl pivalate: vinyl acetate: butyl acrylate = viscosity 1,200 mPas·s, determined by NMR
33:38:29, and the Tg determined by DSC is -
The temperature was 3°C. Next, the above emulsion was subjected to an adhesion test in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 The autoclave used in Example 1 had an average degree of polymerization of 1000.
, 5 parts of partially saponified PVA with a degree of saponification of 88 mol% was dissolved in 85 parts of ion-exchanged water, and 15 parts of vinyl acetate was added to 60 parts.
Polymerization was started using a hydrogen peroxide solution and a Rongalit aqueous solution at a temperature of 35 kg/cm2 under an ethylene pressure. Then, 70 parts of vinyl acetate was added continuously over 3 hours. The analytical values of the obtained emulsion are as follows, and this is used in Example 1.
It was subjected to an adhesion test according to the following. The results are shown in Table 1. Solid concentration: 52.9% Viscosity: 2,600 mPas・s Resin composition: Ethylene; Vinyl acetate = 14:86Tg; 8
°C Example 3 Partially saponified P with average polymerization degree of 800 and saponification degree of 88 mol%
5 parts of VA were dissolved in 85 parts of ion-exchanged water, 65 parts of vinyl pivalate and 21 parts of vinyl acetate were added, and polymerization was carried out at 55°C using hydrogen peroxide and Rongalite under a pressure of 40 kg/cm2 of ethylene. The analytical values of the obtained emulsion were as follows. Solid content concentration: 55.1% Viscosity: 1,900 mPas・s Resin composition: Vinyl pivalate: Vinyl acetate: Ethylene =
64:21:15 Tg: 2°C 10 parts of dibutyl phthalate was added to 100 parts of this emulsion, and the same adhesion test as in Example 1 was conducted. The results are shown in Table 1.

Comparative Example 2 5 parts of partially saponified PVA with an average degree of polymerization of 1000 and a degree of saponification of 88 mol % was dissolved in 85 parts of ion-exchanged water, and 72 parts of vinyl acetate and 21 parts of Veova-10 (manufactured by Shell Chemical) were added. Polymerization was carried out at 60° C. using hydrogen peroxide solution and Rongalite under pressure of 30 kg/cm 2 of ethylene. The analytical values of the obtained emulsion were as follows. Solid content concentration: 53.1% Viscosity: 1300 mPas・s Resin composition: Vinyl acetate: Veova-10: Ethylene =
70:20:10 Tg; 9°C The emulsion was subjected to an adhesion test in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3 Partially saponified P with average polymerization degree of 800 and saponification degree of 88 mol%
Dissolve 5 parts of VA in 85 parts of ion-exchanged water, add 30 parts of vinyl pivalate and 45 parts of vinyl acetate, and dissolve 55 parts of ethylene.
Polymerization was carried out at 50°C using hydrogen peroxide and Rongalit under pressure of kg/cm2. The analytical values of the obtained emulsion were as follows. Solid concentration: 54.7% Viscosity: 2100 mPas・s Resin composition: Vinyl pivalate: Vinyl acetate: Ethylene =
30:43:27 Tg; -12°C Table 1 shows the results of the adhesion test for this emulsion.

0012

[Table 1]

[0013]

Effects of the Invention As is clear from the above examples, the adhesive of the present invention whose main component is a copolymer emulsion of vinyl pivalate and an ethylenically unsaturated monomer having a glass transition temperature of 5°C or higher. has extremely high water resistance compared to conventional adhesives.

Claims (4)

[Claims] 1. An adhesive whose main component is a copolymer emulsion of vinyl pivalate and an ethylenically unsaturated monomer having a glass transition temperature of -10° C. or higher. [Claim 2] The ethylenically unsaturated monomer is ethylene,
The adhesive according to claim 1, which is one or more monomers selected from the group of vinyl acetate and acrylic ester. 3. The copolymer composition in the copolymer is 5 to 90% by weight of vinyl pivalate units and 5 to 8 vinyl acetate units.
Adhesive according to claim 1, characterized in that it contains 0% by weight and 5-50% by weight of ethylene units. 4. The copolymer composition in the copolymer is 5 to 90% by weight of vinyl pivalate units and 5 to 8 vinyl acetate units.
0% by weight and 5-50% by weight of acrylic acid ester units
The adhesive according to claim 1.