JPH04342784A - Room temperature-setting pressure-sensitive adhesive - Google Patents

Abstract

PURPOSE:To provide the title adhesive capable of spray coating and of developing adequate cohesive force or tack characteristics after room temperature setting dispensing with any special setting treatment, also excellent in storage stability. CONSTITUTION:The objective adhesive consisting of an alcoholic dispersion containing (A) 100 pts.wt. of an acrylic polymer mainly comprising an acrylic 4-18C alkyl ester and also containing 0.001-1wt.%, based on the main ingredient, of an alkoxysilane ingredient and (B) 10-300 pts.wt. of internally crosslinked acrylic polymer particles produced from unsaturated monomer mixture containing >=50wt.% of an acrylic 1-18C alkyl ester.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention can be spray coated, contains an alkoxysilane component, cures at room temperature,
Furthermore, the present invention relates to an acrylic pressure-sensitive adhesive that can be stored stably.

0002

[Prior Art] Conventionally, pressure-sensitive adhesives that can be spray-coated and are advantageous for application to porous surfaces, uneven surfaces, etc. have been developed using methods such as stirring or redispersing emulsions or aqueous suspensions. It is known that adhesive components are dispersed in organic solvents (Japanese Patent Publication No. 46-12640, Japanese Unexamined Patent Application Publication No. 61/1989).
-241375 Publication, Special Publication No. 1-12765)
. The reason why it is called a dispersion type is that a solution type tends to form a coating state like a spider's web.

However, in any conventional pressure-sensitive adhesive that can be spray-coated, in order to develop sufficient cohesive force or adhesive properties in the spray-coated adhesive layer, a cross-linking agent is required. It is necessary to perform special curing treatment such as heat treatment when formulating the product, and there are problems in that the simplicity of spray coating cannot be fully utilized or that it cannot be used on objects to be coated that cannot be hardened. .

0004

[Problems to be Solved by the Invention] The present invention can be applied by spray coating, is cured at room temperature, and exhibits sufficient cohesive force or adhesive properties without the need for special curing treatment, and does not pose any practical problems. The goal is to develop a pressure-sensitive adhesive that can be stored without any problems.

[0005]

[Means for Solving the Problems] The present invention uses an acrylic acid-based alkyl ester whose alkyl group has 4 to 18 carbon atoms as a main component, and an alkoxysilane component containing 0.0% of the main component.
An internally crosslinked acrylic polymer comprising 100 parts by weight of an acrylic polymer containing 01 to 1% by weight and an unsaturated monomer containing at least 50% by weight of an acrylic acid alkyl ester whose alkyl group has 1 to 18 carbon atoms. Combined particles 10-3
The present invention provides a room temperature-curable pressure-sensitive adhesive characterized by comprising an alcohol dispersion containing 0.00 parts by weight.

[0006]

[Operation] The acrylic polymer containing an alkoxysilane component cures at room temperature without the need for heat treatment, develops cohesive force, and exhibits excellent adhesive properties together with internally crosslinked acrylic polymer particles. Further, by forming a dispersion using an alcohol solvent, it can be spray coated and has excellent storage stability.

[0007]

Exemplification of Constituent Elements of the Invention The pressure-sensitive adhesive of the present invention has an acrylic acid-based alkyl ester having an alkyl group of 4 to 18 carbon atoms as a main component, and an alkoxysilane component in an amount of 0.001 to 1% of the main component. % by weight of acrylic polymer.

Examples of the acrylic acid-based alkyl esters include butyl group, amyl group, isoamyl group, 2-ethylhexyl group, isooctyl group, isononyl group, decyl group, dodecyl group, lauryl group, and stearyl group. Examples include alkyl esters of acrylic acid or methacrylic acid having an alkyl group of 4 to 18. When polymerizing an acrylic polymer, one or more acrylic acid alkyl esters are used.

In the present invention, for the purpose of modifying the obtained acrylic polymer, the number of carbon atoms in the alkyl group is 4 to 1.
One or more other suitable unsaturated monomers having the same weight or less as the acrylic acid alkyl ester of No. 8 can be used in combination. Examples of commonly used unsaturated monomers include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, and crotonic acid; Acrylic acid alkyl esters having a functional organic group such as a hydroxyethyl group, hydroxypropyl group, or glycidyl group, vinyl esters such as vinyl acetate or vinyl propionate, styrene or its like. Examples include derivatives such as acrylonitrile, methacrylonitrile, acrylamide, and methacrylamide.

In the present invention, an alkoxysilane component is copolymerized into the acrylic polymer in order to impart room temperature curability. The content of the alkoxysilane component is 0.001 to 1% by weight, preferably 0.01 to 0.0% by weight of the acrylic acid alkyl ester in which the alkyl group has 4 to 18 carbon atoms.
It is assumed to be 5% by weight. If the content is less than 0.001% by weight, the effect of improving cohesive force by room temperature curing will be poor, and if it exceeds 1% by weight, the shelf life will be shortened and it will be impractical.

Examples of the alkoxysilane monomers used in the copolymerization include those having a radically polymerizable reactive group such as an acryloyl group, a methacryloyl group, a vinyl group, or a mercapto group in the molecule. Specific examples thereof include γ-methacryloxypropyltrimethoxysilane, vinyltriethoxysilane, and γ-mercaptopropyltrimethoxysilane.

[0012] Acrylic polymers can be prepared using organic peroxides such as bis(4-t-butylcyclohexyl) peroxydicarbonate and benzoyl peroxide;
It is carried out by an appropriate method such as a solution polymerization method using a known radical polymerization initiator such as an azo compound such as 2,2-azobisisobutyronitrile or 2,2-azobis(2,4-dimethylvaleronitrile). It's fine. During polymerization, it is preferable to use a polymerization medium containing an alcohol as a component in order to suppress crosslinking of the produced polymer due to the alkoxysilane component.

The pressure-sensitive adhesive of the present invention comprises internally crosslinked acrylic polymer particles using an unsaturated monomer containing at least 50% by weight of an acrylic acid alkyl ester having an alkyl group having 1 to 18 carbon atoms. It uses

The particle diameter of the acrylic polymer particles to be used may be determined as appropriate, but it is preferably 0.1 to 200 μm in view of the sprayability and the thickness of the adhesive layer formed. The appropriate amount of the acrylic polymer particles to be used is 10 to 300 parts by weight, particularly 20 to 200 parts by weight, per 100 parts by weight of the acrylic polymer. If the amount used is less than 10 parts by weight, the sprayability will be poor, and if it exceeds 300 parts by weight, the room temperature curability will be poor.

[0015] The internally crosslinked acrylic polymer particles may be formed by any suitable method, such as by pulverizing the internally crosslinked acrylic polymer. A preferred method in terms of simplicity and the like is a method in which particles are formed while preparing the acrylic polymer. Any method can be used to obtain the particulate acrylic polymer. Examples include emulsion polymerization, suspension polymerization, and dispersion polymerization. A dispersion obtained by a dispersion polymerization method using an organic medium, especially an alcoholic medium has the advantage that it can be used as it is in the preparation of the pressure-sensitive adhesive of the present invention.

Acrylic polymer particles obtained by emulsion polymerization, suspension polymerization, etc. using water as a medium are used after being separated from water. The separation may be carried out by any suitable method, such as coagulation using methanol or an electrolyte, filtration in the case of large particles such as suspended polymer particles, or replacing water with an organic solvent.

The internal crosslinking of the acrylic polymer particles may be carried out by any known method, in addition to a method in which internal crosslinking is carried out during polymerization using an organic peroxide as a polymerization initiator. Examples include a method of copolymerizing a small amount of a crosslinking monomer such as a polyfunctional allyl monomer, and a method of crosslinking by absorbing a crosslinking agent such as peroxide into prepared uncrosslinked polymer particles. It will be done. The degree of internal crosslinking is preferably 20 to 97% based on the gel fraction from the viewpoint of spray coating properties.

[0018] Examples of the unsaturated monomers used for preparing the acrylic polymer particles include those exemplified for the above-mentioned acrylic polymer. In that case, the amount of one or more unsaturated monomers consisting of acrylic acid alkyl esters having an alkyl group of 1 to 18 carbon atoms is 50% by weight to 1% by weight.
00% by weight is used.

The pressure-sensitive adhesive of the present invention comprises an acrylic polymer and an alcoholic dispersion containing internally crosslinked acrylic polymer particles. Examples of its preparation include adding and dispersing internally crosslinked acrylic polymer particles to a polymerization solution of an acrylic polymer, or mixing a polymerization solution of an acrylic polymer with an organic solvent dispersion of internally crosslinked acrylic polymer particles. The method may be carried out by any appropriate method, such as a method in which an acrylic polymer is polymerized and prepared in the presence of internally crosslinked acrylic polymer particles. In preparing the pressure-sensitive adhesive, various additives commonly used in pressure-sensitive adhesives, such as crosslinking agents such as epoxy compounds and tackifiers, may be added.

The alcoholic solvent used in the dispersion medium has an alcohol content of 5% by weight or more, especially 10% to 10% by weight.
Preferably, it dissolves the acrylic polymer at 100% by weight. If the alcohol content is less than 5% by weight, crosslinking caused by the alkoxysilane component cannot be sufficiently suppressed, and gelation may occur during storage, resulting in poor spraying.

As the alcohol, lower alcohols such as methanol, ethanol, and (iso)propanol are preferably used. As other solvents that may be used in combination with alcohols, any appropriate solvent may be used.

[0022]

[Effects of the Invention] The pressure-sensitive adhesive of the present invention is composed of an alcohol-based dispersion, and has excellent storage stability without gelation over a long period of time, and has stable spray coating properties. Furthermore, after coating, it cures at room temperature without any special curing treatment such as heating based on the alkoxysilane component, forming a pressure-sensitive adhesive layer with excellent cohesive strength.

[0023]

【Example】

Example 1 75 parts of ethyl acetate (parts by weight, same below), 7 parts of methanol
5 parts, butyl acrylate 95 parts, acrylic acid 5 parts, γ-
A mixture consisting of 0.05 part of methacryloxypropyltrimethoxysilane and 0.2 part of 2,2-azobis(2,4-dimethylvaleronitrile) was placed in a four-necked flask, and after purging with nitrogen, the mixture was heated to 50°C. Solution polymerization was started and then polymerized at 50 to 60°C for 8 hours to obtain an acrylic polymer solution A with a solid content concentration of 40% by weight.

300 parts of ion-exchanged water and 2 parts of sodium dodecylbenzenesulfonate are placed in a four-necked flask and dissolved under stirring, and 0.5 parts of benzoyl peroxide is added to this.
100 parts of butyl acrylate was added and stirred. After the resulting suspension was purged with nitrogen, it was heated to 70°C to initiate suspension polymerization, and then polymerized at 70°C for 6 hours to obtain a suspension polymerization liquid. The solid content concentration of this polymerization liquid is 25% by weight.
It was filtered and washed with water to obtain acrylic polymer particles B having a gel fraction of 65% and an average particle size of about 30 μm.

Next, the above acrylic polymer solution A1
00 parts, 40 parts of acrylic polymer particles B, and 1 part of acetone.
30 parts and 50 parts of methanol were added and stirred to obtain a pressure-sensitive adhesive of the present invention having a solid content concentration of 25% by weight. The above gel fraction is determined by wrapping the acrylic polymer particles in a Teflon membrane with a pore size of 0.2 μm, immersing it in toluene, and leaving it at room temperature for 10 days to remove the insoluble content (gel content) remaining in the Teflon membrane. It was determined by drying and weighing and calculating the ratio (the same applies hereinafter).

Example 2 127.5 parts of ethyl acetate, 22.5 parts of ethanol, 90 parts of 2-ethylhexyl acrylate, 10 parts of acrylic acid,
γ-methacryloxypropyltrimethoxysilane 0.1
A mixture of 1 part and 0.2 parts of 2,2-azobisisobutyronitrile was placed in a four-necked flask, and after purging with nitrogen, the mixture was heated to 60°C.
The mixture was heated to start solution polymerization, and then polymerized at 60 to 75°C for 8 hours to obtain an acrylic polymer solution C having a solid content concentration of 40% by weight.

[0027] Put 300 parts of ion-exchanged water and 1 part of polyvinyl alcohol into a four-necked flask and dissolve them.
, 100 parts of 2-ethylhexyl acrylate in which 0.3 parts of 2-azobisisobutyronitrile and 0.1 parts of trimethylolpropane triacrylate were dissolved were added and stirred. After the resulting suspension was purged with nitrogen, it was heated to 70°C to initiate suspension polymerization, and then polymerized at 70°C for 6 hours to obtain a suspension polymerization liquid. The solid content concentration of this polymerization liquid was 25% by weight, and it was filtered and washed with water to obtain acrylic polymer particles D having a gel fraction of 50% and an average particle size of about 45 μm. Next, 100 parts of the above acrylic polymer solution C, 20 parts of acrylic polymer particles D, 102 parts of acetone, and 18 parts of methanol were added.
A pressure sensitive adhesive of the present invention having a solid content concentration of 25% by weight was obtained.

Example 3 120 parts of ethyl acetate, 30 parts of methanol, 2 parts of acrylic acid
- A mixture consisting of 85 parts of ethylhexyl, 10 parts of vinyl acetate, 5 parts of acrylic acid, 0.5 part of γ-methacryloxypropyltrimethoxysilane, and 0.2 part of 2,2-azobis(2,4-dimethylvaleronitrile). It was placed in a four-necked flask, and after nitrogen purging, it was heated to 50°C to start solution polymerization, and then polymerized at 50 to 60°C for 8 hours to obtain an acrylic polymer solution E with a solid content concentration of 40% by weight. .

Put 150 parts of ion-exchanged water, 3 parts of sodium dodecylbenzenesulfonate, and 0.3 part of ammonium persulfate into a four-necked flask and dissolve them, and add 1 part of glycidyl methacrylate and 0.01 part of trimethylolpropane triacrylate. 99 parts of ethyl acrylate dissolved in
1 part and stirred. The resulting liquid was purged with nitrogen and heated to 60°C to initiate emulsion polymerization, and then polymerized at 70°C for 6 hours to obtain an emulsion polymerization liquid. The solid content concentration of this polymerization solution was 40% by weight, and the gel fraction was 32% by salting out and washing with water.
, Acrylic polymer particles F having an average particle diameter of about 0.4 μm were obtained. Next, 120 parts of acetone was added to 80 parts of the acrylic polymer particles F and stirred, and the resulting dispersion was added to 100 parts of the acrylic polymer solution E, and 21 parts of acetone was added.
6 parts and 84 parts of methanol were added and stirred until the solid content concentration was 2.
0% by weight of the pressure sensitive adhesive of the invention was obtained.

Example 4 75 parts of ethyl acetate, 75 parts of methanol, 2-acrylic acid
95 parts of ethylhexyl, 5 parts of acrylic acid, 0.03 parts of γ-methacryloxypropyltrimethoxysilane, 2,2
-Azobis(2,4-dimethylvaleronitrile) 0.2
The mixture consisting of 50 to 60% of
Polymerization was carried out at 0° C. for 8 hours to obtain an acrylic polymer solution G having a solid content concentration of 40% by weight.

100 parts of methanol, 5 parts of dispersion stabilizer polymer (butyl acrylate/acrylic acid: 90/10),
A mixture consisting of 95 parts of 2-ethylhexyl acrylate, 0.1 part of diallyl terephthalate, and 0.3 part of bis(4-t-butylcyclohexyl) peroxydicarbonate was placed in a four-necked flask and dissolved under stirring. After nitrogen substitution, the mixture was heated to 45° C. to initiate dispersion polymerization, and then polymerized at 50° C. for 10 hours to obtain a milky white dispersion H. The solid content concentration of this dispersion was 50% by weight, the gel fraction of the dispersed polymer (acrylic polymer particles) was 57%, and the average particle diameter was about 8 μm. Next, acrylic polymer particle dispersion H1 was added to 100 parts of the acrylic polymer solution G.
6 parts of acetone, 104 parts of acetone, and 100 parts of methanol were added and stirred to obtain a pressure-sensitive adhesive of the present invention having a solid content concentration of 15% by weight.

Comparative Example 1 A pressure-sensitive adhesive was obtained in accordance with Example 1, except that acrylic polymer solution I containing no γ-methacryloxypropyltrimethoxysilane and having a solid content concentration of 40% by weight was used.

Comparative Example 2 A pressure-sensitive adhesive was prepared in the same manner as in Example 1, except that acrylic polymer solution J with a solid content concentration of 40% by weight, obtained by using 2 parts of γ-methacryloxypropyltrimethoxysilane, was used. I got it.

Comparative Example 3 According to Example 1, the amount of ethyl acetate used was 150 parts,
Acrylic polymer solution K with a solid content concentration of 40% by weight was obtained without using methanol, and 40 parts of acrylic polymer particles B and 180 parts of acetone were added to 100 parts of the acrylic polymer solution K and stirred to obtain a solid content concentration of 25%. % pressure sensitive adhesive was obtained.

Evaluation Test Retention Strength (Cohesive Strength) The pressure-sensitive adhesives obtained in Examples and Comparative Examples were spray-coated onto an aluminum sheet to a thickness of about 50 μm and air-dried.
Leave it at room temperature for a week, then apply it to a stainless steel plate for 20 minutes.
Adhere with adhesive area of mm x 10 mm, 30℃ or 80℃
Below, the time required for the aluminum sheet to fall under a vertical load of 500 g was measured.

Preservability The pressure-sensitive adhesives obtained in Examples and Comparative Examples were sealed and left at room temperature to examine the storage period during which they could be sprayed without gelation.

The above results are shown in Table 1.

[Table 1]

From the table, it can be seen that in the examples of the present invention, excellent cohesive strength was developed by curing by simply leaving at room temperature without any special treatment after spray coating. Furthermore, it can be seen that the pressure-sensitive adhesive of the present invention has excellent storage stability.

Claims (1)

[Claims] 1. 100 parts by weight of an acrylic polymer whose main component is an acrylic alkyl ester with an alkyl group having 4 to 18 carbon atoms, and which contains an alkoxysilane component in an amount of 0.001 to 1% by weight based on the main component; From an alcoholic dispersion containing 10 to 300 parts by weight of internally crosslinked acrylic polymer particles using an unsaturated monomer containing at least 50% by weight of an acrylic acid alkyl ester having 1 to 18 carbon atoms. A room temperature-curing pressure-sensitive adhesive characterized by: