JPH0124429B2 - - Google Patents

Description

[Detailed description of the invention]

This invention is characterized in that a water-dispersed pressure-sensitive adhesive composition made of an acrylic base polymer into which a functional group with a photosensitizing effect has been introduced is applied onto a tape support, dried, and then irradiated with light. The present invention relates to a method of manufacturing an adhesive tape. Conventionally, this type of tape has been manufactured by applying a solution of an acrylic polymer in an organic solvent to the tape support and drying it, but this method requires a large amount of organic solvent and requires a large amount of petroleum resources. There are many problems in terms of pollution prevention, fire safety, etc., and switching to alternative methods is actively being promoted. One such method is water-dispersible pressure-sensitive adhesives. Water-dispersed pressure-sensitive adhesives do not have the above problems;
In addition, it has been widely used because it is easier to achieve thickness accuracy than hot-melt pressure-sensitive adhesives, but since it uses water as a medium, it is difficult for the base polymer and crosslinking agent to become uniform, so it is difficult to maintain stable cohesion. There was a flaw in not being able to obtain it. That is, water-dispersed acrylic pressure-sensitive adhesives have conventionally been used with the addition of crosslinking agents such as polyisocyanate compounds, epoxy resins, melamine resins, peroxides, and metal salts in order to obtain sufficient cohesive strength. However, in either case, emulsion particles consisting of a crosslinking agent dissolved or dispersed in water and a base polymer exist as separate entities in the emulsion, and since the crosslinking agent participates in the crosslinking reaction only with the surface of the emulsion particles, the inside of the emulsion particles As a result, it is difficult to homogenize adhesive properties, especially cohesive force, and it is difficult to obtain a stable product. The above-mentioned difficulty becomes more pronounced as the particle size of the emulsion particles made of the base polymer increases, and in this case, even if a large amount of crosslinking agent is added, sufficient cohesive force cannot be obtained. Moreover, since the above particle size varies considerably depending on conditions such as emulsion polymerization, the cohesive strength and adhesive strength of the adhesive obtained will change due to this variation even when the same crosslinking agent is used in the same amount. However, there was a problem that consistent adhesive properties could not be expected. In order to avoid such problems, a polyfunctional monomer having two or more carbon-carbon unsaturated bonds in one molecule is used as a type of monomer component in the production of polymer emulsions, thereby creating a three-dimensional structure. Attempts have been made to obtain polymer particles that are In other words, the three-dimensional structure aims to improve the cohesive force similar to that of an external crosslinking agent. However, this method has the problem that the degree of three-dimensionalization tends to vary greatly due to slight differences in polymerization operations, and stable cohesive force similar to that obtained with external crosslinking agents cannot be obtained. From this point of view, the inventors have conducted extensive studies and found that a uniform crosslinking reaction occurs within and between polymer particles in a water-dispersed acrylic pressure-sensitive adhesive, resulting in slight variations in the particle diameter of the polymer particles. We have now discovered a method for producing a pressure-sensitive adhesive tape that provides stable cohesive force regardless of the conditions and has excellent adhesive properties. That is, the present invention provides a) an acrylic acid alkyl ester and/or a methacrylic acid alkyl ester, b) a polymerizable unsaturated monomer having a polar group, and c) a polymerizable unsaturated monomer having a photosensitizing functional group. It consists of a monomer, and 0.01 to 0.01 to 0.01 to 100 parts by weight of component c is added to 100 parts by weight of the above-mentioned component a and component b.
A photo-crosslinkable water-dispersed pressure-sensitive adhesive whose base polymer is an acrylic copolymer obtained by emulsion polymerization of a monomer mixture containing 5 parts by weight is applied to a tape support, dried, and then irradiated with light. The present invention relates to a method for producing a pressure-sensitive adhesive tape. In this invention, a functional group that can easily generate radicals by light irradiation, that is, an oil-soluble functional group that has a photosensitizing effect, is uniformly and evenly introduced into each polymer in the water-dispersed polymer particles. Therefore, by coating this on a support, drying it, and then irradiating it with light, uniform crosslinking can be obtained both within and between the polymer particles, and stable cohesive force can be obtained regardless of the size of the polymer particles. Therefore, the pressure-sensitive adhesive tape obtained by this method is superior to the conventional method using a water-dispersed pressure-sensitive adhesive using an external cross-linking agent, even if there is some variation in the particle diameter of the polymer particles. It is possible to obtain high cohesive force and stable quality. In addition, according to the method of the present invention, compared to the above-mentioned conventional method using a water-dispersed pressure-sensitive adhesive, the crosslinking reaction proceeds only when irradiated with light, so the pot life can be freely adjusted, and changes in tape properties over time. It has characteristics such as less Furthermore, the advantage of using water-dispersed pressure-sensitive adhesives is that there is no risk of fire compared to solution-based adhesives, and it is easier to achieve the same thickness accuracy as solution-based adhesives compared to hot-melt adhesives. , is extremely useful industrially. The a component used in this invention includes ethyl acrylate, butyl acrylate, diacrylic acid
- Use one or more of acrylic acid alkyl esters such as ethylhexyl and isooctyl acrylate, and methacrylic acid alkyl esters such as ethyl methacrylate and butyl methacrylate. Note that up to 20% by weight of component a may be replaced with other unsaturated monomers copolymerizable with component a, such as vinyl monomers such as vinyl acetate, acrylonitrile, and methacrylonitrile. As the component b used in this invention, an acrylic polymerizable unsaturated monomer having a polar group such as a carboxyl group, a hydroxyl group, or an amino group is used, such as acrylic acid, methacrylic acid, itaconic acid, acrylic acid, etc. Examples include acid 2-hydroxyethyl ester and acrylic acid dimethylaminoethyl ester. The amount of component b to be used is usually that of the total amount of component a and component b.
It is preferable to adjust the amount to 0.2 to 20% by weight. The c component used in this invention has the following general formula; (However, R is hydrogen or a methyl group, and P is a functional group with a photosensitizing effect.) It is a monomer that is expressed by changing a compound with a photosensitizing effect to a derivative having a hydroxyl group, and then acrylic Obtained by reaction with acid or methacrylic acid. Examples of compounds having photosensitizing effects include aromatic ketones, aromatic aldehydes, aromatic carboxylic acids, and thioxanthone compounds having photosensitizing effects such as benzophenone, anthraquinone, and benzoin. As a specific example of this c component, for example, the following structural formula This compound is commercially available from UCB under the trade name UVECRYL P-36 and can be easily used. The amount of component c to be used is 0.01 to 5 parts by weight, preferably 0.02 to 2 parts by weight, based on 100 parts by weight of the total amount of components a and b. If the amount of component c used is less than 0.01 part by weight, the crosslinking of the pressure-sensitive adhesive layer formed will be insufficient and the cohesive force will be low, which is not preferable. Furthermore, if the amount of component c used exceeds 5 parts by weight, the degree of crosslinking of the adhesive layer becomes too high and the adhesive strength decreases, which is not preferable. Emulsion polymerization of the monomer mixture consisting of components a, b, and c is carried out by adding appropriate emulsifiers and polymerization initiators to water together with the monomer mixture, and adding a chain transfer agent if necessary. The reaction is usually carried out at 50 to 85 DEG C. for 3 to 10 hours under a nitrogen stream, thereby obtaining the photocrosslinkable water-dispersed pressure-sensitive adhesive of the present invention. As the emulsifier used here, any known nonionic or anionic emulsifier can be used, and the amount is preferably 5 parts by weight or less per 100 parts by weight of the acrylic copolymer. If the amount used exceeds 5 parts by weight, the adhesion strength decreases, resulting in poor water resistance. In addition, as a polymerization initiator, persulfates such as ammonium persulfate and potassium persulfate, hydrogen peroxide, redox catalysts of these and sodium bisulfite, metal salts, amines, etc., and organic peroxides such as benzoyl peroxide are used. can also be used. The amount of polymerization initiator used is 100% of the unsaturated monomer.
0.01 to 5 parts by weight, preferably 0.05 parts by weight
~2 parts by weight. The molecular weight of the obtained acrylic copolymer is usually about 100,000 to 2,000,000, preferably 200,000 to 100,000.
If necessary, use a molecular weight regulator such as lauryl mercaptan or thioglycolic acid, or adjust the amount of polymerization initiator, polymerization temperature, polymerization time, etc. so that the molecular weight is within the above range. It is better to do so. The acrylic copolymer obtained as described above has a photosensitizing functional group in its molecule, and can be uniformly crosslinked both within and between emulsion particles when irradiated with light. The dispersion liquid of this acrylic copolymer after emulsion polymerization may be used as it is as the pressure-sensitive adhesive of the present invention, but various additives may be added thereto as necessary. Examples of such additives include photoactive crosslinking agents such as ethylene glycol dimethacrylate and trimethylpropane triacrylate. This photoactive crosslinking agent is activated by receiving excitation energy from actinic rays or a photosensitizer and leads to crosslinking of the acrylic copolymer, thereby increasing the crosslinking efficiency. The amount added is usually 0 to 100 parts by weight of the acrylic copolymer.
The amount is preferably 10 parts by weight, preferably 0 to 3 parts by weight. If too much is added, the crosslinking density of the pressure-sensitive adhesive will increase, resulting in a high degree of three-dimensionality and loss of tackiness, which is not preferable. In addition, in order to further improve the initial adhesive strength (tack) of the pressure-sensitive adhesive layer formed by light irradiation, a tackifying resin, a softener such as a plasticizer, or a low-molecular-weight acrylic material with an average molecular weight of 8,000 to 20,000 may be used. A system polymer may also be added. The amount of these additives is preferably up to 50 parts by weight per 100 parts by weight of the acrylic copolymer; if the amount is too large, the cohesive strength, heat resistance, and other properties of the pressure-sensitive adhesive layer will be impaired. These additives can be used directly or by dropping a solution dissolved in a small amount of an organic solvent into water containing 1 to 5 parts by weight per 100 parts by weight of the additive, stirring, and emulsifying the water-dispersed type of the present invention. By adding it to pressure-sensitive adhesives, it can be easily and uniformly dispersed. Furthermore, if necessary, polyvinyl alcohol and other emulsion stability improvers, thickeners, and the like can be added. The photocrosslinkable water-dispersed pressure-sensitive adhesive obtained in this way has a low viscosity and has a solid content of about 30 to 60%.
Even when the concentration is as high as 10% by weight, a uniform thickness (usually 10~
It can be coated with a thickness of 100μm). By heating and drying after application and irradiating with light, the above-mentioned adhesive is crosslinked, and a pressure-sensitive adhesive tape with excellent adhesive properties, particularly excellent cohesion, and stable quality can be obtained. The light rays emitted here usually have a wavelength range.
Ultraviolet rays of approximately 180 to 400 nm are preferred, and sources include low-pressure, medium-pressure, and high-pressure mercury lamps. Generally, the appropriate light irradiation time is 3 to 120 seconds based on a 400W high-pressure mercury lamp. Examples of this invention are shown below. In addition, in the following, parts mean parts by weight. Also,
In order to investigate the adhesive properties of the obtained pressure sensitive adhesive tape, the adhesive force and cohesive force were measured as follows. <Adhesive strength> Cut the pressure-sensitive adhesive tape into 20 mm width pieces and press them to a stainless steel plate once with a 2 kg roller. crimp 30
After 18 minutes, measure the adhesive strength at 180° at 20°C using a Schottper type peel tester at a speed of 300mm/min. <Cohesive force> 10mm x 20 pressure sensitive adhesive tape on Bakelite plate
2 mm, apply a load of 900 g at 40°C, and measure the displacement distance after 1 hour. Example 1 70 parts of butyl acrylate, 25 parts of 2-ethylhexyl acrylate, 5 parts of acrylic acid, UVECRYL
P-36 (the aforementioned polymerizable unsaturated monomer having a photosensitizing functional group) 0.5 parts, dialkylsulfosuccinate sodium salt (emulsifier) 3
parts, potassium persulfate 0.3 parts and ion exchange water 100 parts
An acrylic polymer emulsion was obtained by reacting the mixture consisting of the following parts at 70°C under a nitrogen stream for 8 hours. The average molecular weight of the polymer in this emulsion was 1 million, and the average particle size was about 1700 Å. This acrylic polymer emulsion was made into a water-dispersed pressure-sensitive adhesive as it was, and this was applied to a thickness of 25 μm.
It was coated on a support made of polyester film to a dry thickness of 80 μm, dried at 110°C for 10 minutes, and then irradiated with a 400W high-pressure mercury lamp at an irradiation distance of 20cm for 30 seconds, 45 seconds, and 60 seconds. By doing so, a pressure-sensitive adhesive tape according to the present invention was produced. Comparative Example 1 A mixture consisting of 70 parts of butyl acrylate, 25 parts of 2-ethylhexyl acrylate, 5 parts of acrylic acid, 3 parts of dialkyl sulfosuccinate sodium salt, 0.3 part of potassium persulfate, and 100 parts of ion-exchanged water was heated with nitrogen. An acrylic polymer emulsion was obtained by reacting at 70° C. for 8 hours under air flow. The average molecular weight of the polymer in this emulsion is
1 million, and the average particle diameter was about 1600 Å. To this acrylic polymer emulsion, 0.5 parts of UVECRYL P-36 (mentioned above) dissolved in 2 parts of toluene was added to 100 parts of the solid content of the emulsion and stirred uniformly to form a water-dispersed pressure-sensitive adhesive. This was applied onto a 25 μm thick polyester film to a dry thickness of 80 μm, dried at 110°C for 10 minutes, and then irradiated with a 400 W high pressure mercury lamp at a distance of 20 cm for 30 seconds, 45 seconds, and 60 seconds. A comparative pressure-sensitive adhesive tape was prepared by irradiating it with light. Comparative Example 2 In the polymer emulsion obtained in Comparative Example 1,
0.5 parts, 1 part, and 2 parts of water-soluble melamine resin are added to 100 parts of the solid content of this emulsion to make a water-dispersed pressure-sensitive adhesive, and this is applied onto a 25 μm thick polyester film to a dry thickness of 80 μm. It was applied as follows and dried at 130°C for 10 minutes to obtain a pressure-sensitive adhesive tape. Comparative Example 3 In the polymer emulsion obtained in Comparative Example 1,
0.5 parts, 1 part and 2 parts of benzoyl peroxide dissolved in 2 parts of toluene were added to 100 parts of the solid content of this emulsion and stirred uniformly to form a water-dispersed pressure sensitive adhesive. It was coated onto a thick polyester film to a dry thickness of 80 μm, and dried at 150° C. for 10 minutes to obtain a pressure-sensitive adhesive tape. When the adhesive properties of the pressure sensitive adhesive tapes obtained in Example 1 and Comparative Examples 1 to 3 above were evaluated, the results shown in Tables 1 and 2 below were obtained.

【table】

[Table] Example 2 70 parts of butyl acrylate, 25 parts of 2-ethylhexyl acrylate, 5 parts of acrylic acid, UVECRYL
A mixture of 0.5 parts of P-36 (mentioned above), 3 parts of dialkyl sulfosuccinate sodium salt, and 25 parts of ion-exchanged water was mixed with potassium persulfate under a nitrogen stream.
An acrylic polymer emulsion was obtained by dropping the mixture into a mixture of 0.3 parts and 75 parts of ion-exchanged water for 8 hours to react. The average molecular weight of the polymer in this emulsion was 1 million, and the average particle diameter was about 2400 Å. This acrylic polymer emulsion was made into a water-dispersed pressure-sensitive adhesive as it was, and this was applied to a thickness of 25 μm.
It was applied to a polyester film with a dry thickness of 80 μm, dried at 130°C for 10 minutes, and then
30 seconds at 20cm irradiation distance with a 400W high-pressure mercury lamp,
Pressure-sensitive adhesive tapes according to the invention were prepared by irradiating with light for 45 seconds and 60 seconds. Comparative Example 4 A mixture consisting of 70 parts of butyl acrylate, 25 parts of 2-ethylhexyl acrylate, 5 parts of acrylic acid, 3 parts of dialkylsulfosuccinate sodium salt, and 25 parts of ion-exchanged water was mixed with 0.3 parts of potassium persulfate under a nitrogen stream. An acrylic polymer emulsion was obtained by dropping the mixture over 8 hours into a mixture of 75 parts of ion-exchanged water and 75 parts of ion-exchanged water.
The average molecular weight of the polymer in this emulsion is 100
The average particle diameter was approximately 2,400 Å. To this acrylic polymer emulsion, 0.5 UVECRYL P-36 (mentioned above) dissolved in 2 parts of toluene per 100 parts solid content of this emulsion was added.
of the mixture and stirred uniformly to obtain a water-dispersed pressure-sensitive adhesive. This was applied onto a 25μm polyester film to a dry thickness of 80μm, and heated at 110℃.
After drying for 10 minutes, heat with a 400W high-pressure mercury lamp for 20 minutes.
Comparative pressure-sensitive adhesive tapes were prepared by irradiating with light for 30 seconds, 45 seconds, and 60 seconds at an irradiation distance of cm. Comparative Example 5 In the polymer emulsion obtained in Comparative Example 4,
0.5 parts, 1 part and 2 parts of water-soluble melamine resin are added to 100 parts of the solid content of this emulsion to make a water-dispersed pressure sensitive adhesive, and this is applied onto a 25 μm thick polyethylene film to a dry thickness of 80 μm. It was applied as follows and dried at 130°C for 10 minutes to obtain a pressure-sensitive adhesive tape. Comparative Example 6 In the polymer emulsion obtained in Comparative Example 4,
0.5 parts, 1 part and 2 parts of benzoyl peroxide dissolved in 2 parts of toluene are added to 100 parts of the solid content of this emulsion and stirred uniformly to form a water-dispersed pressure sensitive adhesive. 25μm
It was coated onto a thick polyester film to a dry thickness of 80 μm, and dried at 150° C. for 10 minutes to obtain a pressure-sensitive adhesive tape. When the adhesive properties of the pressure sensitive adhesive tapes obtained in the above Example 2 and Comparative Examples 4 to 6 were evaluated, the results shown in Tables 3 and 4 below were obtained.

【table】

【table】

[Table] As is clear from the comparison between Tables 1 and 2 and Tables 3 and 4 above, the photo-crosslinkable water-dispersed pressure-sensitive adhesive of the present invention was used to support tape support. Pressure-sensitive adhesive tapes that are applied to the body, dried, and irradiated with light are crosslinked uniformly both within and between the polymer particles in the polymer emulsion, making them stable regardless of the particle size of the polymer particles. It can be seen that it is possible to easily provide a pressure-sensitive adhesive tape that provides cohesive strength, stable quality, and excellent adhesive properties.

Claims (1)

[Claims] 1 Consisting of a) acrylic acid alkyl ester and/or methacrylic acid alkyl ester, b) a polymerizable unsaturated monomer having a polar group, and c) a polymerizable unsaturated monomer having a functional group having a photosensitizing effect. , photocrosslinking using as a base polymer an acrylic copolymer obtained by emulsion polymerization of a monomer mixture containing 0.01 to 5 parts by weight of component c based on 100 parts by weight of the total amount of components a and b. 1. A method for producing a pressure-sensitive adhesive tape, which comprises applying a water-dispersed pressure-sensitive adhesive of the type on a tape support, drying it, and then irradiating it with light.