JPH04320471A - Photopolymerizable adhesive composition, pressure-sensitive adhesive prepared by using the same, and adhesive sheet coated therewith - Google Patents

Abstract

PURPOSE:To obtain the title composition improved in adhesion to a (non)polar adherend and cohesive force by mixing a specified monomer mixture with a phenol-modified rosin tackifying resin, a photopolymerization initiator, and a polyfunctional acrylate monomer. CONSTITUTION:A monomer mixture is obtained by mixing 70-99wt.% monomer mainly consisting of an alkyl acrylate monomer with an alkyl group having 1-14 carbon atoms on the average with 30-1wt.% copolymerizable monomer having a polar group. The title composition is obtained by mixing 100 pts.wt. said mixture with 2-40 pts.wt. phenol-modified rosin tackifying agent selected from among a phenol-modified rosin (glycerol ester), a phenol-modified rosin pentaerythritol ester and a phenol-modified rosin glycol ester, 0.1-5 pts.wt. photopolymerization initiator and 0.2-5 pts.wt. polyfunctional acrylate monomer.

Description

Detailed Description of the Invention [0001] [Industrial Application Field] The present invention provides an adhesive composition containing a photopolymerizable acrylic monomer, and a pressure-sensitive adhesive composition by photopolymerizing this adhesive composition. Related to pressure-sensitive adhesives with adhesive properties and cohesive strength, and adhesive sheets in the form of sheets, tapes, etc., with this pressure-sensitive adhesive applied on one or both sides of a base material. It is. [Prior Art] Generally, acrylic pressure-sensitive adhesives are
It has been prepared by solution polymerization of monomers mainly composed of alkyl acrylate monomers, but due to the safety of organic solvents and environmental hygiene constraints, emulsion polymerization and photopolymerization have recently been adopted. It is becoming widely used. Among these, photopolymerized pressure-sensitive adhesives are particularly advantageous in terms of safety and environmental improvement, since no solvents are used in the manufacturing process. As such photopolymerizable pressure-sensitive adhesives, for example, Japanese Patent Publication No. 58-500130 (US Pat. No. 4,364,972) discloses pressure-sensitive adhesives that exhibit high adhesion to automobile paints. A monomer mixture of an alkyl acrylate monomer and N-vinyl-2-pyrrolidone is used as an adhesive, and a tackifier and a photoinitiator are added to this to photopolymerize it. Are known. [0004] Furthermore, JP-A-57-47308 (US Pat. No. 4,243,500) discloses a tackifier comprising a monofunctional unsaturated acrylate monomer and a substantially saturated tackifying resin polymer. , an amorphous elastomeric block copolymer, and a pressure sensitive adhesive containing a radiation sensitive initiator. [0005] In these photopolymerizable pressure-sensitive adhesives, the tackifier added thereto is an important component in imparting good adhesive strength and adhesive strength to the adhesive after photopolymerization. For example, in the above-mentioned Japanese Patent Application Laid-Open No. 57-47308, about 5 parts per 100 parts by weight of acrylate monomer.
A large amount of 0 to 250 parts by weight is used. However, since tackifiers generally act as chain terminators in photopolymerization reactions, if they are used in large amounts, they inhibit polymerization, lowering the molecular weight of acrylic polymers and reducing adhesive strength. This causes a decrease in cohesive force. [0007] For this reason, it is desirable to select and use a tackifier that has the lowest possible photopolymerization inhibiting effect as a tackifier to be added to this type of adhesive. The publication describes an aliphatic polymer resin whose number average molecular weight, polydispersity index, glass transition temperature, and solubility parameter are set within specific ranges, and JP-A-2-18485 describes a hydrogenated rosin ester resin. It has been proposed to use tackifiers based on tackifiers. [0008] These tackifiers hardly act as chain terminators during photopolymerization, and are certainly effective in suppressing polymerization inhibition. but,
Recently, adherends have become more diverse, and adhesion to a wide variety of adherends has become more important than ever. In this respect, known pressure sensitive adhesives using tackifiers such as those described above still lack good adhesion from non-polar adherends such as polypropylene to polar adherends such as stainless steel. It is not possible to respond adequately and is not necessarily satisfactory. In view of the above-mentioned conventional circumstances, the present invention provides a photopolymerizable acrylic pressure-sensitive adhesive that has good adhesion to various polar or non-polar adherends and has a large cohesive force. The aim is to obtain drugs. Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that an adhesive composition to be photopolymerized contains a specific material different from the conventional one. When a specific amount of tackifier is blended, it is possible to photopolymerize well without polymerization inhibition caused by chain transfer, which is the case with conventional methods. The present invention was completed based on the knowledge that a pressure-sensitive adhesive with good adhesion to adherends and satisfactory cohesive force can be obtained. That is, the present invention comprises the following four components a to d;
~99% by weight and 30-1% of polar group-containing copolymerizable monomer
100 parts by weight of a monomer mixture consisting of % by weight b) 2 to 40 parts by weight of a phenol-modified rosin tackifier c) 0.1 to 5 parts by weight of a photopolymerization initiator d) Polyfunctional acrylate monomer This invention relates to a photopolymerizable adhesive composition characterized in that it contains 0.2 to 5 parts by weight. The present invention also provides an acrylic pressure-sensitive adhesive obtained by photopolymerizing the above photopolymerizable adhesive composition by irradiation with light such as ultraviolet rays to impart pressure-sensitive adhesive properties and cohesive strength; This invention relates to adhesive sheets in the form of sheets, tapes, etc., in which the pressure-sensitive adhesive is provided on one or both sides of a base material. Structure and operation of the invention The monomer mixture as component a in the present invention comprises a main monomer mainly composed of an alkyl acrylate monomer and a copolymerizable monomer containing a polar group. The main monomer of the former is alkyl acrylate monomer as the main component, as well as general acrylic pressure-sensitive adhesives such as vinyl acetate and styrene. Various vinyl monomers known as modifying monomers can be used in a proportion of usually 30% by weight or less based on the main monomers. As the alkyl acrylate monomer, methyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, Isononyl (meth)
Any alkyl group having a carbon number of 1 to 14, such as acrylate, can be used. As the polar group-containing copolymerizable monomer, (
Unsaturated acids such as meth)acrylic acid, itaconic acid, and 2-acrylamidopropanesulfonic acid, hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate, etc. used. The proportion of the main monomer mainly composed of alkyl acrylate monomer and the polar group-containing copolymerizable monomer is 70 to 99% by weight for the former and 30% by weight for the latter. ~1
It is particularly preferable that the former be 90 to 98% by weight and the latter be 10 to 2% by weight. Outside these ranges, favorable results in terms of adhesive properties cannot be obtained. The phenol-modified rosin-based tackifier as component b in the present invention can be prepared, for example, by adding a resol type phenol formaldehyde resin to the rosin, or by adding a polyhydric alcohol to the rosin. The phenol modification improves chemical resistance, water resistance, etc., and increases the molecular weight, resulting in a high softening point. Examples of such phenol-modified rosin tackifiers include phenol-modified rosin, phenol-modified rosin glycerin ester, phenol-modified rosin pentaerythritol ester, and phenol-modified rosin glycerin. Commercially available products include Sumilite Resin PR12603 manufactured by Sumitomo Durez Co., Ltd. and Tamanol 80 manufactured by Arakawa Chemical Industry Co., Ltd.
3. Haliphenol P-140 manufactured by Harima Kasei Co., Ltd. and the like. When such a phenol-modified rosin tackifier is used, very good adhesion can be obtained to both non-polar and polar adherends, and the cohesive force can also be satisfied. becomes. On the other hand, if rosin, rosin ester, hydrogenated rosin, etc. that are not modified with phenol are used, good adhesion to various adherends cannot be expected, and cohesive strength is also poor. Become. The amount of this phenol-modified rosin tackifier used is usually 2 to 100 parts by weight of component a.
The amount is preferably 40 parts by weight, preferably 2 to 30 parts by weight, and more preferably 2 to 20 parts by weight. If the amount is less than 2 parts by weight, or if it is more than 40 parts by weight, a pressure-sensitive adhesive that satisfies both adhesive strength and cohesive strength to various polar and non-polar adherends cannot be obtained. As the photopolymerization initiator for component c in the present invention, benzoin ethers such as benzoin methyl ether and benzoin isopropyl ether, substituted benzoin ethers such as anisole methyl ether, 2.2-
Diethoxyacetophenone, 2,2-dimethoxy-2-
Substituted acetophenones such as phenylacetophenone, 2
Substituted alpha-ketols such as -methyl-2-hydroxypropiophenone, aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride, 1-phenyl-1,1-propanedione-2-(o- Photoactive oximes such as ethoxycarbonyl)-oxime are used. The amount of such a photopolymerization initiator used is usually 0.1 to 5 parts by weight per 100 parts by weight of component a.
The amount is preferably 0.1 to 3 parts by weight, and may be appropriately selected within this range depending on the degree to which it acts as a chain terminator for the phenol-modified rosin tackifier used. If the amount of the photopolymerization initiator used is too small, polymerization inhibition by the tackifier cannot be suppressed and the polymerization rate decreases, whereas if it is too large, the polymerization rate increases but the molecular weight decreases and cohesive force is insufficient. Polyfunctional acrylate as component d in the present invention
Examples of the monomer include trimethylolpropane triacrylate, pentaerythritol tetraacrylate, 1,2-ethylene glycol diacrylate,
1,6-hexanediol diacrylate, 1,12-
A difunctional or higher functional polyalkyl acrylate monomer such as dodecanediol diacrylate is used. The amount of the polyfunctional acrylate monomer used varies somewhat depending on the number of functional groups, etc., but is generally 0.2 to 5 parts by weight, preferably 0.2 to 5 parts by weight, per 100 parts by weight of component a. The amount is preferably 2 to 3 parts by weight. If a polyfunctional acrylate monomer is used in such a range, even if a decrease in cohesive force is observed due to chain transfer to the tackifier, this will be compensated for by the crosslinking effect of the monomer, resulting in good results. Cohesive force is maintained. The photopolymerizable adhesive composition of the present invention has the above-mentioned a.
It contains a monomer mixture as component, a phenol-modified rosin tackifier as component b, a photopolymerization initiator as component c, and a polyfunctional acrylate monomer as component d. , the monomer mixture of component a can be prepolymerized to some extent using a part of the photopolymerization initiator of component c. [0026] In addition to the above four components a to d, this photopolymerizable adhesive composition also contains, as optional components, a plasticizer,
Various conventionally known additives such as softeners, fillers, pigments, and dyes can be appropriately blended within the range that does not inhibit the photopolymerizability. [0027] In the present invention, such a photopolymerizable adhesive composition is coated directly onto an adherend or once coated on a release paper, and then applied at a rate of 400 to 1500 mj/c.
By photopolymerizing the adhesive by irradiating it with ultraviolet rays of about m2, it is possible to obtain a tackified acrylic pressure-sensitive adhesive that itself has pressure-sensitive adhesive properties. [0028] Instead of coating on an adherend or release paper, various base materials such as a synthetic resin film such as a polyester film or a fiber base material may be used, and the coating may be applied on one or both sides of this base material. By photopolymerizing this in the same manner as described above, adhesive sheets in the form of sheets or tapes can be obtained. The thickness of the adhesive layer at this time is arbitrary. The photopolymerized acrylic pressure-sensitive adhesive thus obtained exhibits good adhesion to various polar or non-polar adherends, and also exhibits a large cohesive force. Furthermore, the phenol-modified rosin tackifier used exhibits a high softening point and exhibits good properties in terms of heat-resistant cohesive strength. The reason why such excellent adhesive properties are obtained is not necessarily clear, but in the presence of a phenol-modified rosin tackifier, monomers mainly composed of alkyl acrylate monomers By photopolymerizing the acrylic polymer mixture to make it sticky, a graft product between the polymer and the tackifier was created, which improved the compatibility of the two, and changed the flexibility of the acrylic polymer skeleton. It is presumed that this is the case. [0031] As described above, in the present invention, a monomer mixture containing an alkyl acrylate monomer as a main component is combined with a photopolymerization initiator and a polyfunctional acrylate monomer. By containing a specific amount of a phenol-modified rosin-based tackifier and photopolymerizing it, it exhibits good adhesion to various polar or non-polar adherends and has a large cohesive force. Acrylic pressure-sensitive adhesive and its adhesive sheet that also exhibits
We can provide the following items. [Examples] Next, examples of the present invention will be described in more detail. In addition, in the following, parts mean parts by weight. Furthermore, the photopolymerization rate during the production of the adhesive tape and the characteristics of the adhesive tape were evaluated using the following method. <Polymerization rate> A sample X1 g (approximately 0.1 g) of which the polymerization rate is to be measured is taken and stored in a dryer at 130° C. for 3 hours, and then the weight of the sample X2 g is measured again. From the weights of X1 and X2, polymerization rate = (X
2/X1)×100(%). <Adhesive Strength> Adhesive strength (g/20 mm width) was measured according to JIS Z-1522 using a stainless steel plate and a polypropylene plate as adherends. <Creep resistance deviation distance> Stainless steel plate with BA finish on the surface (30 mm x 120 mm x 3.0
An evaluation sample (width 10 mm) was attached to one end of the stainless steel plate in the longitudinal direction so that the adhesive area was 20 mm x 10 mm, and after being left for 30 minutes, it was heated to 40 °C for 20 minutes. Heat treated for minutes. next,
The stainless steel plate was set vertically so that the side with the sample attached was facing downward, and a load of 500 g was applied to the other end of the sample. In this state, the displacement distance of the sample from the stainless steel plate per hour at 40°C was measured using a creep tester. Example 1 90 parts of 2-ethylhexyl acrylate, 1 part of acrylic acid
0 parts and 0.05 parts of 2,2-dimethoxy-2-phenylacetophenone were charged into a four-necked flask and exposed to ultraviolet light in a nitrogen atmosphere to partially photopolymerize, thereby forming an oligomer. A syrup containing (viscosity 30 poise) was obtained. To 100 parts of this partially polymerized syrup, 0.5 parts of trimethylolpropane triacrylate, 0.3 parts of additional photopolymerization initiator, and 10 parts of phenol-modified rosin were uniformly mixed. , a photopolymerizable adhesive composition was prepared. This adhesive composition is coated on the release-treated surface of a polyethylene terephthalate film with a thickness of 25 μm that has been subjected to a low-adhesion release treatment, and then a polyethylene film with a thickness of 25 μm is applied on top of this. After coating with terephthalate film as a base material, ultraviolet rays are applied at 900 mj/cm.
2 irradiation and photopolymerization. Thereafter, it was cut to a width of 20 mm to obtain an adhesive tape with an adhesive layer having a thickness of 50 μm. Example 2 Example 1 except that 10 parts of phenol-modified rosin glycerin ester was used instead of phenol-modified rosin.
A photopolymerizable adhesive composition was prepared in the same manner as in Example 1, and an adhesive tape was produced using this in the same manner as in Example 1. Example 3 A photopolymerizable adhesive composition was prepared in the same manner as in Example 1, except that 10 parts of phenol-modified rosin pentaerythritol ester was used in place of the phenol-modified rosin. Using this, an adhesive tape was produced in the same manner as in Example 1. Comparative Example 1 A photopolymerizable adhesive composition was prepared in the same manner as in Example 1, except that no additional photopolymerization initiator was added to the partially polymerized syrup, and this was used in Example 1. An adhesive tape was produced in the same manner. However, the photopolymerization rate during the production of the adhesive tape was as low as 82%, and it was found that an adhesive tape worthy of evaluation could not be obtained due to the adverse effects of the residual monomer. Comparative Example 2 A photopolymerizable adhesive composition was prepared in the same manner as in Example 1, except that no phenol-modified rosin was added. A tape was made. Comparative Example 3 A photopolymerizable adhesive composition was prepared in the same manner as in Example 1, except that 10 parts of perhydrogenated rosin ester was used in place of the phenol-modified rosin. Example 1 using
Adhesive tape was prepared in the same manner as above. Comparative Example 4 A photopolymerizable adhesive composition was prepared in the same manner as in Example 1, except that 10 parts of an alicyclic saturated hydrocarbon resin was used in place of the phenol-modified rosin. An adhesive tape was produced in the same manner as in Example 1. Reference Example 1 90 parts of 2-ethylhexyl acrylate, 1 part of acrylic acid
0 parts, 0.4 parts of 2,2'-azobisisobutyronitrile, and 250 parts of ethyl acetate were charged into a four-necked flask, and polymerized at 60° C. for 10 hours under a nitrogen atmosphere. Next, to this polymer solution, 10 parts of phenol-modified rosin and 2 parts of a trifunctional isocyanate compound were added to 100 parts of the polymer to prepare a pressure-sensitive adhesive solution. Next, apply this adhesive solution to a thickness of 25 μm.
It was coated on a polyethylene terephthalate film of 100 mL to a thickness of 50 μm after drying, and dried at 100° C. for 5 minutes. Thereafter, the adhesive tape was cut into the same tape width as in Example 1 to obtain an adhesive tape. Reference Example 2 Reference Example 1 except that 10 parts of phenol-modified rosin glycerin ester was used instead of phenol-modified rosin.
A pressure-sensitive adhesive solution was prepared in the same manner as above, and an adhesive tape was produced in the same manner as in Reference Example 1 using this solution. Reference Example 3 A pressure-sensitive adhesive solution was prepared in the same manner as in Reference Example 1, except that 10 parts of phenol-modified rosin pentaerythritol ester was used in place of the phenol-modified rosin. An adhesive tape was produced in the same manner as in Reference Example 1. Reference Example 4 A pressure-sensitive adhesive solution was prepared in the same manner as in Reference Example 1, except that no phenol-modified rosin was added, and using this solution, an adhesive tape was prepared in the same manner as in Reference Example 1. A sample was prepared. The adhesive properties of each of the adhesive tapes of Examples 1 to 3, Comparative Examples 2 to 4, and Reference Examples 1 to 4 were investigated, and the results were as shown in Table 1 below. . In addition, for the adhesive tapes of Examples 1 to 3 and Comparative Examples 2 to 4, the polymerization rate of photopolymerization at the time of tape production was also described. Examples 4 to 10 The amount of phenol-modified rosin (tackifier), the amount of photopolymerization initiator added, and the polyfunctional acrylate monomer (trimethylolpropane triacrylate) Seven types of photopolymerizable adhesive compositions were prepared in the same manner as in Example 1, except that the amounts of An adhesive tape was made using the following method. Characteristic evaluations of these adhesive tapes are shown in Table 3 below. Example 11 The monomer composition of the partially photopolymerized syrup was changed to 10 parts of 2-ethylhexyl acrylate, 10 parts of n-butyl acrylate,
Example 1 except that 85 parts of acrylic acid and 5 parts of acrylic acid were used.
A photopolymerizable adhesive composition was prepared in the same manner as in Example 1, and an adhesive tape was produced using this in the same manner as in Example 1. Example 12 Example 1 except that 10 parts of phenol-modified rosin glycerin ester was used instead of phenol-modified rosin.
A photopolymerizable adhesive composition was prepared in the same manner as in Example 1, and an adhesive tape was produced in the same manner as in Example 1 using this composition. Example 13 A photopolymerizable adhesive composition was prepared in the same manner as in Example 11, except that 10 parts of phenol-modified rosin pentaerythritol ester was used in place of the phenol-modified rosin. Using this, an adhesive tape was produced in the same manner as in Example 1. Comparative Example 5 A photopolymerizable adhesive composition was prepared in the same manner as in Example 11 except that no phenol-modified rosin was added.
Using this, an adhesive tape was produced in the same manner as in Example 1. Comparative Example 6 A photopolymerizable adhesive composition was prepared in the same manner as in Example 11, except that 10 parts of perhydrogenated rosin ester was used in place of the phenol-modified rosin. An adhesive tape was produced in the same manner as in Example 1. Comparative Example 7 A photopolymerizable adhesive composition was prepared in the same manner as in Example 11, except that 10 parts of an alicyclic saturated hydrocarbon resin was used in place of the phenol-modified rosin. An adhesive tape was produced in the same manner as in Example 1. Examples 11-13 and Comparative Examples 5-
The adhesive properties and the photopolymerization rate during tape preparation were investigated for each adhesive tape No. 7, and the results were as shown in Table 4 below. [0062] From the above results, Examples 1 to 13 of the present invention
The adhesive tape has superior adhesive strength to adherends ranging from polar to non-polar, and also has good cohesive strength, compared to the conventionally known adhesive tapes of reference and comparative examples. I understand.

Claims (4)

[Claims] Claim 1: The following four components a to d; a) 70 to 99% by weight of a main monomer consisting mainly of an alkyl acrylate monomer in which the alkyl group has an average of 1 to 14 carbon atoms; and 100 parts by weight of a monomer mixture consisting of 30 to 1% by weight of a polar group-containing copolymerizable monomer b) 2 to 40 parts by weight of a phenol-modified rosin tackifier c) 0 parts by weight of a photopolymerization initiator .1～
5 parts by weight d) A photopolymerizable adhesive composition comprising 0.2 to 5 parts by weight of a polyfunctional acrylate monomer. 2. The phenol-modified rosin tackifier of component b is phenol-modified rosin, phenol-modified rosin glycerin ester, phenol-modified rosin pentaerythritol ester, or phenol-modified rosin glycerin. 2. The photopolymerizable adhesive composition according to claim 1, comprising a polyester. 3. A pressure-sensitive adhesive obtained by photopolymerizing the photopolymerizable adhesive composition according to claim 1 or 2. 4. Adhesive sheets comprising the pressure-sensitive adhesive according to claim 3 on one or both sides of a base material.