JP2680342B2 - Peelable adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of use) The present invention relates to a peelable pressure-sensitive adhesive composition. More specifically, the pressure-sensitive adhesive composition of the present invention is applied to a film or the like to produce a peelable pressure-sensitive adhesive film or the like. When used as a surface protective material for various base materials and the like, the present invention relates to a peelable pressure-sensitive adhesive composition in which the adhesive force between the adherend and the pressure-sensitive adhesive layer does not change over time and the surface of the adherend has very little contamination. Is.

(Prior Art) Generally, an adhesive protective film is attached to a metal plate such as stainless steel or aluminum, or a plastic plate such as an acrylic plate or a polycarbonate plate in order to prevent contamination during transportation, storage or processing. When using these plate materials, it is necessary to peel off the protective film, but the adhesive force between the plate material and the adhesive layer significantly increases over time, the protective film becomes very difficult to peel off, and in some cases there is residual glue on the plate material. It has the drawback of occurring. In order to solve this drawback, the following three methods have been proposed. The first is a method of devising the composition and composition of the pressure-sensitive adhesive resin. For example, in JP-A-61-47772, an acrylic polymer having a weight average molecular weight of 200,000 or more is used.
A resin composition for pressure-sensitive adhesives, which is composed of 0 to 30,000 acrylic polymers, has been proposed. The second method is to add a surfactant to the pressure-sensitive adhesive, which is disclosed in JP-A-55-10841 and JP-A-59.
-58072, JP-A-61-108685 and the like. The third method is to add a substance having a small cohesive force to the pressure-sensitive adhesive. In JP-A-57-17077, a pressure-sensitive adhesive composition containing a fluorine-containing compound is used, and in JP-A-55-160075. A method of compounding a silicone resin and silicone oil with an acrylic pressure-sensitive adhesive resin is further described in
JP-A 60-197780 proposes a composition prepared by mixing a silicone pressure-sensitive adhesive with an acrylic pressure-sensitive adhesive resin.

(Problems to be Solved by the Invention) One of the causes of the change in the adhesive force over time is that the wetting of the pressure-sensitive adhesive layer on the adherend gradually progresses, and from a microscopic point of view, it is composed of a large number of uneven surfaces. It is generally known that the anchoring effect that the contact area between the adherend surface and the pressure-sensitive adhesive layer increases. Further, the present inventors have made various investigations and obtained the following findings. That is, among the components and functional groups contained in the pressure-sensitive adhesive, those having an affinity action with the adherend due to polar force or hydrogen bond are concentrated or reversed at the interface with the adherend over time, and the interface It was confirmed that the binding was increased. Therefore, at the initial point of time when the adherend and the pressure-sensitive adhesive layer were bonded together, almost complete interfacial peeling occurred at the time of peeling, but with time, it changed to peeling with cohesive failure near the surface of the pressure-sensitive adhesive layer. It was found that the adhesive strength increased. It can be seen that if the above phenomenon can be prevented, the change with time of the adhesive force can be suppressed. However, in the proposals disclosed heretofore, it cannot be said that the change with time of the adhesive force is sufficiently suppressed and the contamination of the adherend is sufficiently suppressed, and further improvement of the performance is required.
The reason for this is that, for example, when the composition or composition of the pressure-sensitive adhesive resin is improved, the nature of the pressure-sensitive adhesive which is accompanied by the progress of wetting over time and the polar functional group necessary for increasing the cohesive force of the resin There is an unavoidable existence with.
When a surfactant is added to the pressure-sensitive adhesive, the surfactant gradually bleeds to the contact surface between the adherend and the pressure-sensitive adhesive layer, weakening the adhesive strength with the adherend, increasing the adhesive strength. Although it has a preferable effect for preventing it, it cannot exert the effect of suppressing the inversion of the functional group of the pressure-sensitive adhesive resin and the concentration of the component having an affinity for the adherend at the interface. In addition, migration of the surfactant to the adherend is also a problem. In addition, when a fluorine-containing compound, a silicone resin, or a silicone oil is blended with the pressure-sensitive adhesive resin, the cohesive force of the pressure-sensitive adhesive resin is reduced and the compatibility of the pressure-sensitive adhesive resin with the added compound is Therefore, the cohesive destruction of the pressure-sensitive adhesive and the added compound cannot be prevented from being transferred to the adherend to some extent, and further improvement is required.

The present inventors, on the basis of the recognition of the above problems and findings, as a result of intensive studies, increase the wettability of the adhesive, and further, the effect of inverting the functional group and concentrating the affinity component with the adherend. It was found that if a barrier layer that can be effectively blocked is formed on the surface of the pressure-sensitive adhesive layer, the change in the adhesive force with time can be reduced, and the contamination of the adherend can be reduced, and in order to achieve this object, an acrylic pressure-sensitive adhesive The present invention was completed by confirming that a peelable pressure-sensitive adhesive composition containing a specific amount of a polysiloxane group-containing polymer having a specific structure and forming a specific surface composition is particularly effective.

(Means for Solving the Problems) The peelable pressure-sensitive adhesive composition of the present invention contains an acrylic pressure-sensitive adhesive and a polysiloxane group-containing polymer having a specific structure, and the amount of the polysiloxane group-containing polymer is acrylic. X-ray photoelectron analysis measured under the condition that the amount of photoelectrons escaped from the surface of the pressure-sensitive adhesive layer is 90 degrees with respect to 100 parts by weight of the pressure-sensitive adhesive, and the surface of the pressure-sensitive adhesive layer is 90 degrees. The device has a molar ratio of silicon atoms to carbon atoms of 0.15 to 0.45.
To form a composition in the range of.

It is essential that the polysiloxane group-containing polymer in the present invention has a structure that is surface active and is miscible with the acrylic pressure-sensitive adhesive. By having these two functions, the polysiloxane component is oriented on the surface at the time of forming the pressure-sensitive adhesive layer, and a layer composed of an aggregate of polysiloxane is formed on the outermost surface to concentrate the affinity component with the adherend and functional group. Plays the role of a barrier layer that prevents the inversion of When the surface of the pressure-sensitive adhesive layer is entirely composed of a polysiloxane layer, the property of the pressure-sensitive adhesive main body that it has adhesiveness to the adherend disappears, and when the amount of polysiloxane component on the surface of the pressure-sensitive adhesive layer is too small, it functions as a barrier layer. Appropriate amount of polysiloxane is required as it will decrease and the adhesive strength will change over time. An X-ray photoelectron analyzer (hereinafter abbreviated as ESCA) is known as an effective means for measuring the surface composition. This ES
When CA is used to measure the pressure-sensitive adhesive composition of the present invention under the condition that the escape angle of photoelectrons from the pressure-sensitive adhesive layer surface is 90 degrees, the molar ratio of silicon atom to carbon atom (hereinafter [Si] / [C] (Abbreviated) is in the range of 0.15 to 0.45. [Si] / [C] is 0.
When it is 15 or more, when the adherend and the pressure-sensitive adhesive layer are stuck together, wetting of the pressure-sensitive adhesive layer on the adherend progresses quickly,
The slow progress of wetting after pasting is small, and as a result, the phenomenon of the anchoring effect progressing over time can be suppressed.

[Si] / [C] on the surface of the pressure-sensitive adhesive layer is determined by the content and structure of the polysiloxane group-containing polymer in the pressure-sensitive adhesive composition. As long as a surface composition of [Si] / [C] of 0.15 to 0.45 can be formed, there is no effect on the suppression of the change over time in the adhesive strength of the polysiloxane-containing polymer content, but in terms of maintaining the cohesive strength of the adhesive. , 10 parts by weight or less based on 100 parts by weight of the acrylic pressure-sensitive adhesive. If it is less than 0.1 parts by weight, it becomes difficult to set [Si] / [C] to 0.15 or more, so 0.1 parts by weight or more is necessary.

It is essential that the polysiloxane group-containing polymer of the present invention is surface-active and has miscibility with the acrylic pressure-sensitive adhesive. It is surface active because [Si] / [C] forms a composition of 0.15 to 0.45 on the surface of the pressure-sensitive adhesive layer. Miscibility with acrylic pressure-sensitive adhesives is essential to prevent contamination of adherends, especially silicone. That is, since the acrylic pressure-sensitive adhesive and the polysiloxane group-containing polymer are miscible, it is possible to prevent the polysiloxane layer from being detached from the pressure-sensitive adhesive layer and transferred to the surface of the adherend. Further, the surface-active and better miscible material has an advantage that a more uniform polysiloxane layer is formed on the surface of the pressure-sensitive adhesive layer.

To impart miscibility with acrylic pressure-sensitive adhesives,
The structure of the polysiloxane group-containing polymer is preferably one in which a polymer having miscibility with an acrylic pressure-sensitive adhesive and a polysiloxane are bonded. The miscible polymer portion in the polysiloxane group-containing polymer is particularly preferably formed from a copolymer of methacrylic acid, methacrylic acid ester, acrylic acid ester, fatty acid vinyl ester, or the like. In order to introduce a polysiloxane into a copolymer composed of these radically polymerizable monomers, considering the ease of adjusting the amount of polysiloxane groups introduced and the ease of synthesis, polysiloxanes having radically polymerizable functional groups are introduced. Preference is given to using siloxanes. In this case, the polysiloxane has a molecular weight of 50.
When it is 00 or more, the reactivity decreases, so it is effective to use a polysiloxane having radically polymerizable functional groups at both ends in combination in order to increase the introduction rate of polysiloxane. Therefore, the polysiloxane group-containing polymer of the present invention has a constitutional unit of 5 to 85 based on one kind or a mixture of two or more kinds of the compounds represented by the following general formulas (I) to (II).
Polysiloxane group-containing copolymer consisting of 15% to 95% by weight of structural units based on one or more selected from the group consisting of methacrylic acid, methacrylic acid ester, acrylic acid, acrylic acid ester, and fatty acid vinyl ester. (Hereinafter referred to as polysiloxane group-containing polymer A), or a block copolymer comprising a polysiloxane group-containing copolymer portion and a polysiloxane group-free polymer portion, wherein the polysiloxane group-containing copolymer portion is Is 5 to 85% by weight of a structural unit based on one kind or a mixture of two or more kinds of compounds represented by the following general formulas (I) to (II) and methacrylic acid, methacrylic acid ester, acrylic acid, acrylic acid ester, fatty acid vinyl Consisting of 15 to 95% by weight of a structural unit based on a monomer selected from the group consisting of esters,
The polymer portion containing no polysiloxane group is a structural unit based on one or a mixture of two or more monomers selected from the group consisting of methacrylic acid, methacrylic acid ester, acrylic acid, acrylic acid ester, and fatty acid vinyl ester. The following polysiloxane group-containing polymer (hereinafter referred to as polysiloxane group-containing polymer B) is particularly preferable.

General formula Wherein R ₁ is a hydrogen atom or a methyl group, R ₂ is a methyl group,
Ethyl group, phenyl group or (Wherein, R ₅ is a hydrogen atom, a phenyl group or _{C p H 2P + 1, R} 6
Represents a methyl group, an ethyl group or a phenyl group, respectively.
m is an integer of 1 or more, and p is an integer of 1 to 10. ), R ₃
Represents a hydrogen atom, a phenyl group or C _{PH 2P + 1} , and R ₄ represents a methyl group, an ethyl group or a phenyl group, n is an integer of 1 or more, and p is an integer of 1 to 10.

General formula Wherein R ₁ is a hydrogen atom or a methyl group, R ₂ is a methyl group,
Ethyl group, phenyl group or (Wherein, R ₅ is a hydrogen atom, a phenyl group or a _{C P H 2P + 1, R} 6
Represents a methyl group, an ethyl group or a phenyl group, respectively.
m is an integer of 1 or more, and p is an integer of 1 to 10. ), R ₃
Represents a hydrogen atom, a phenyl group or C _{PH 2P + 1} , respectively,
n is an integer of 1 or more, and p is an integer of 1 to 10. R ₂ , R ₃ and R ₄ in the general formulas (I) and (II) may be the same or different among the substituents defined above.
When the number average molecular weight of the polysiloxane is 300 or less, surface activity does not occur in the obtained polysiloxane group-containing polymer, and when the number average molecular weight exceeds 50,000, it becomes difficult to introduce the polysiloxane and the surface activity ability decreases. There is a tendency. The number average molecular weight is preferably 500 or more and 40,000 or less, and more preferably 1,000 or more and 30,000 or less. The polysiloxane of the general formula (I) is commercially available.
For example, trade names FM0711, FM0715, FM0721, FM0725 (Chisso Corporation) and the like correspond to this compound.

The polysiloxane of the general formula (II) can be obtained by a generally known reaction. For example, in the presence of a basic catalyst such as triethylamine or pyridine, 1 mol of a silanol polysiloxane at both ends that can be obtained as a commercial product [manufactured by Chisso Corporation, PS series, etc.] (In the formula, R ₁ represents a hydrogen atom or a methyl group, and R ₂ and R ₃ each represent a methyl group, an ethyl group, or a phenyl group.) Two moles are reacted in a temperature range from room temperature to about 60 ° C. The compound obtained corresponds to the compound of the general formula (II). In addition, Is a known compound and can be obtained by reacting an allyl (meth) acrylate with a silicon compound. There is no limitation on the weight ratio of the polysiloxane represented by the general formulas (I) and (II), and since the surface activity can be expressed as the introduced amount of the polysiloxane group, the polysiloxane group-containing polymer A or the polysiloxane group-containing polymer A can be used. The polysiloxane group-containing polymer portion in the siloxane group-containing polymer B may be 5% by weight or more. Further, when the introduction amount of the polysiloxane group exceeds 85% by weight, the miscibility with the acrylic pressure-sensitive adhesive in the case of the polysiloxane group-containing polymer A decreases, and in the case of the polysiloxane group-containing polymer B, The preferable range is 5% by weight to 85% by weight because the micelles are formed during the synthesis, and the effective barrier layer cannot be obtained when the pressure-sensitive adhesive layer is formed.

Further, if the polysiloxane group is present in the polysiloxane group-containing polymer A or in the polysiloxane group-containing copolymer portion of the polysiloxane group-containing polymer B in an amount of 5% by weight or more, the pressure-sensitive adhesive composition of the present invention The presence of polysiloxane does not hinder the surface activity, but rather the free polysiloxane is aligned with the polysiloxane group-containing polymer on the surface of the pressure-sensitive adhesive layer, forming a barrier layer that suppresses the change in adhesive strength over time. May have an advantageous effect on. Therefore, in some cases, it is not necessary to remove the unreacted polysiloxane, and in some cases, it is effective to include the polysiloxane in the pressure-sensitive adhesive composition. However, in this case, in order to impart surface activity and prevent silicone contamination of the adherend after sticking the pressure-sensitive adhesive layer to the adherend, free polysiloxane is used in the polymerization system during the synthesis of the polysiloxane group-containing polymer. It is essential to exist in. By being present in the polymerization system, the free siloxane is strongly incorporated into the polysiloxane micelle, so that the surface activity can be maintained and the adherend can be prevented from being contaminated with silicone. Significant silicone contamination occurs when the polysiloxane group-containing polymer and free polysiloxane are included during formulation of the composition. When the free polysiloxane is contained, it may have any structure as long as it is a polysiloxane miscible with the general formulas (I) to (II). However, in order to maintain the surface activity and prevent silicone contamination of the adherend, 100 parts by weight of the polysiloxane group-containing copolymer portion in the polysiloxane group-containing polymer A or polysiloxane group-containing polymer B is used. It is preferably 50 parts by weight or less.

The composition of the polymer miscible with the acrylic pressure-sensitive adhesive which is one of the components forming the polysiloxane group-containing polymer in the present invention is the same as that of the acrylic pressure-sensitive adhesive constituting the pressure-sensitive adhesive composition. Accordingly, it is appropriately selected so that miscibility can be expressed. Whether or not the miscibility is good can be determined by visual observation after mixing the acrylic pressure-sensitive adhesive and the polysiloxane group-containing polymer to form a film. That is,
If the film becomes transparent or if it is not transparent and there is no separation when mixed and a uniform film is obtained, it is judged that the miscibility is good. In order to exhibit miscibility with an acrylic pressure-sensitive adhesive, one or more monomers selected from methacrylic acid, methacrylic acid ester, acrylic acid, allyl acid ester, and fatty acid vinyl ester are copolymerized. Is particularly preferred.

For example, methyl (meth) acrylate [methyl (meth) acrylate means methyl methacrylate or methyl acrylate. The same applies hereinafter. ] Lower alkyl (meth) acrylates such as ethyl (meth) acrylate, n-propyl (meth) acrylate and glycidyl (meth) acrylate; n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, Higher (meth) lauryl (meth) acrylate, stearyl (meth) acrylate, etc.
Acrylate: Fatty acid vinyl such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate and the like, hydroxyl group-containing (meth) acrylic such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, etc. It is suitable to use an acid ester, (meth) acrylic acid or the like. Further, other vinyl type monomers can be copolymerized to the extent that the miscibility with the acrylic pressure-sensitive adhesive is not impaired.

In order to suppress the change of the adhesive amount with time, the higher the glass transition temperature of the polymer component which imparts the miscibility, the better the result.Therefore, the amount of methyl methacrylate used should be within the range in which the miscibility can be maintained. It is preferable to increase the size.

The ratio of the polysiloxane group-containing copolymer part to the polysiloxane group-free polymer part in the polysiloxane group-containing polymer B is not particularly limited, but is 25/7 by weight.
It is preferably 5 to 90/10. When the content of the polysiloxane group-containing copolymer portion is 25% by weight or less, the surface activity tends to decrease, and the ability to form a barrier layer on the surface of the pressure-sensitive adhesive layer tends to decrease. On the other hand, if it exceeds 90%, the physical properties are almost the same as those of the polysiloxane group-containing copolymer A, and the effect of forming a block copolymer decreases.

The synthesis of the polysiloxane group-containing polymer in the present invention can be performed by a known method. For example, the polysiloxane group-containing polymer can be synthesized by ordinary radical polymerization. Further, the polysiloxane group-containing polymer B is obtained, for example, by two-step polymerization using polymeric peroxide as an initiator. That is, for example, the following polymeric peroxides Is used to polymerize one or more monomers capable of forming a polymer portion miscible with the acrylic pressure-sensitive adhesive.
At this time, the amount of active oxygen in the polymeric peroxide is set to about 50.
%, The polymer containing a peroxy bond can be obtained by stopping the polymerization. Further, using this as an initiator, one or more polysiloxanes represented by the above general formulas (I) and (II), which can become a polysiloxane group-containing copolymer portion, and other monomers The polysiloxane group-containing polymer B can be obtained by copolymerizing

In the present invention, the purpose is achieved by the pressure-sensitive adhesive layer surface formed from the pressure-sensitive adhesive composition having a specific composition, for which purpose the structure and content of the polysiloxane group-containing polymer can be adjusted appropriately. Therefore, the structure of the acrylic pressure-sensitive adhesive is not particularly limited as long as it has a performance as a pressure-sensitive adhesive.

For example, as a resin constituent component used in an acrylic resin, an acrylic acid alkyl ester, a methacrylic acid alkyl ester as a main constituent component as necessary, a hydroxyl group-substituted acrylic acid alkyl ester, a hydroxyl group-substituted methacrylic acid ester, an alkylene glycol acrylic acid ester, Any of alkylene glycol methacrylic acid ester, acrylamide type, methacrylamide type, dialkylaminoalkyl acrylic acid ester, dialkylaminoalkyl methacrylic acid ester, acrylic acid, methacrylic acid and the like can be used. As the alkyl group, one having 1 to 8 carbon atoms is usually used. The adhesive resin may be a mixture of the acrylic resin and other known adhesive resins. The other resin may be any of natural rubber, synthetic rubber, vinyl acetate and the like.

The pressure-sensitive adhesive composition of the present invention may be added with a crosslinking agent such as an isocyanate compound, a melamine compound, an epoxy compound, a metal chelate, etc. Further, titanium oxide generally added to the pressure-sensitive adhesive, a pigment such as talc, or a thickener. , Stabilizers, tackifiers, etc. can be added. Further, the pressure-sensitive adhesive composition of the present invention has a resin solid content of 35 to 35 using an organic solvent.
It is preferable to adjust it in the range of 50% by weight. The organic solvent is not particularly limited as long as it does not significantly impair the temporal stability of the pressure-sensitive adhesive composition or the solubility of the pressure-sensitive adhesive layer-forming component. For example, a ketone solvent such as methyl ethyl ketone or methyl isobutyl ketone, an ester solvent such as ethyl acetate, or an aromatic solvent such as toluene or xylene can be used.

The pressure-sensitive adhesive composition of the present invention, polyester, polyethylene, synthetic resin film or cloth such as polyvinyl chloride,
An adhesive product can be prepared by using paper, metal foil or the like as a support. These adhesive products can be used as so-called surface protection films, for example, metal plates such as stainless steel and aluminum, or plastic plates such as acrylic plates and polycarbonate plates.

(Effect of the invention) The most important feature of the present invention is that a barrier layer is formed on the surface of the pressure-sensitive adhesive layer to prevent concentration of affinity components with respect to the adherend and inversion of functional groups. When the body and the pressure-sensitive adhesive layer are in contact with each other, wetting progresses promptly, and the anchoring effect thereafter becomes less likely to progress.

Therefore, the adhesive force between the adherend and the pressure-sensitive adhesive layer is prevented from increasing with time, and the contamination of the adherend can be suppressed, and the peelable pressure-sensitive adhesive composition is far superior to conventional ones. is there.

(Examples) Next, the present invention will be described with reference to Examples and Comparative Examples. It should be noted that the numbers of parts and% in the respective production examples, examples and comparative examples are based on weight.

Production Example 1 (A) Synthesis of peroxy bond-containing weight body A reactor equipped with a thermometer, a stirrer and a reflux condenser was charged with 57 g of methyl ethyl ketone and heated to 70 ° C. while blowing nitrogen gas, and 57 g of methyl ethyl ketone was added to methacrylic acid. Methyl 48g * A) A mixed solution of Mn5000 was charged over 2 hours, and a polymerization reaction was performed for 4 hours. The polymerization conversion of methyl methacrylate is
The residual monomer was measured by gas chromatography (GS) and found to be 96%. Next, methyl ethyl ketone was removed from the polymer solution under reduced pressure at room temperature using an evaporator, and the obtained polymer solid was pulverized by a pulverizer until it became fine powder. Further, 20 g of the obtained fine powder was charged into the reactor, 300 g of n-hexane was added, and the mixture was stirred at room temperature for 20 hours to extract unreacted polysiloxane.

After filtering the fine powder, n-hexane was recovered from the recovered n-hexane solution.
The hexane was distilled off to obtain 5.3 g of a viscous compound. As a result of NMR analysis and GPC analysis, it was revealed that the viscous compound contained 15% by weight of low molecular weight polymethylmethacrylate and 85% by weight of unreacted polysiloxane.
As a result of NMR analysis, the fine powder taken out by filtration was found to have a weight ratio of polymethyl methacrylate and polysiloxane of about 75/25.
It became clear that it was a polymer consisting of This fine powder had an active oxygen content of 0.14% and was shown to have a peroxy bond. The number average molecular weight in terms of polystyrene measured by GPC was 21,000.

(B) Synthesis of block copolymer 14 g of the fine powder obtained in (A) above, from which unreacted polysiloxane was removed, 7 g of methyl methacrylate, and 29 g of toluene were mixed and dissolved, and then charged into an ampoule purged with nitrogen and shaken. The reaction was carried out at 70 ° C. for 4 hours and further at 80 ° C. for 4 hours to synthesize a block copolymer. The obtained polymer solution was colorless and transparent. The measurement of residual methyl methacrylate by GC revealed that the polymerization conversion was 98%, and the GPC measurement revealed that the number average molecular weight was 32,000. The resulting polymer solution is reprecipitated with methanol and dried
R analysis indicated that the weight ratio of polymethyl methacrylate to polysiloxane was about 82/18. From these results, the obtained polymer was a block copolymer composed of polymethyl methacrylate (70/30 by weight) in which polysiloxane was grafted in a branched manner and polymethyl methacrylate. It was found that the weight ratio of both polymer parts in the polymer was about 70/30. Dissolve this block copolymer in toluene,
A weight percent solution was prepared.

Production Example 2 Prepared in (A) of Production Example 1 Instead of * A) In all cases, the block copolymer was synthesized in the same manner as in Production Example 1 except that Mn5000 was charged. The weight ratio of polymethylmethacrylate to polysiloxane in the peroxy bond-containing polymer analyzed after removing unreacted polysiloxane in the same manner as in Production Example 1 was about 67/33. The active oxygen content was 0.14%, and the number average molecular weight was 34,000. Further, from the result of analysis after the synthesis of the block copolymer, it was found that the block copolymer was composed of polymethyl methacrylate and a polymer portion in which polysiloxane was bonded in a branched manner and polymethyl methacrylate. It was found that the weight ratio of the polymer part was about 70/30. The number average molecular weight was 42,000. This block copolymer was dissolved in toluene to prepare a 20 wt% solution.

Examples 1 and 2, Comparative Examples 1 to 5 Adhesion between an adhesive film and an adherend prepared by using an adhesive composed of the polysiloxane group-containing polymer synthesized in Production Examples 1 and 2 and an acrylic pressure-sensitive adhesive. The change of force with time and the degree of contamination on the surface of the adherend after peeling the adhesive film were compared with those of the acrylic pressure-sensitive adhesive to which a surfactant or polysiloxane having a number average molecular weight of 5000 was added. Butyl acrylate / vinyl acetate / acrylic acid (preparation composition: 92 /
5/3 weight ratio) Pressure sensitive adhesive consisting of copolymer (solid content concentration:
40%, solvent composition: toluene / ethyl acetate = 1/1 weight ratio,
In the following, referred to as pressure-sensitive adhesive A), a polysiloxane group-containing polymer synthesized in Production Examples 1 or 2, or a surfactant and a predetermined amount of polydimethylsiloxane, and Coronate L
After adding 2 parts (made by Nippon Polyurethane) to 100 parts of the pressure-sensitive adhesive A solution, toluene was added to prepare a 30% solution.
Then, a polyethylene film (manufactured by Okura Industry Co., Ltd., film thickness 60 μ) subjected to corona discharge treatment was applied using an applicator so that the dry film thickness was 25 μ. After that, aging was performed at 60 ° C. for 20 hours to obtain an adhesive film. Then, an adhesive film cut into a width of 25 mm was attached to a sufficiently degreased stainless steel mirror plate (SUS 304, manufactured by Nippon Test Panel) by reciprocating once with a rubber roller weighing 2 kg. The initial adhesive strength was measured within 2 hours after pressure bonding. After that, it was measured after leaving it at 60 ° C. for a predetermined time. The adhesive force is a 180 ° peel force (measurement temperature: 23 ° C) measured at a peeling speed of 300 mm / min. Also,
The surface composition analysis of the pressure-sensitive adhesive layer and the adherend (stainless steel mirror surface plate) was performed using ESCA750 and ESCAPAC760 manufactured by Shimadzu. The measurement is performed when the escape angle of photoelectrons from the adhesive layer or the adherend is 90.
It went under the condition of degree. Table 1 shows the obtained results.

From the results shown in Table 1, the pressure-sensitive adhesive composition of the present invention forms an excellent pressure-sensitive adhesive layer with less change in adhesive strength over time than with the addition of a surfactant or polysiloxane and less contamination of the adherend. It is clear. Further, as shown in Comparative Example 5, the pressure-sensitive adhesive layer surface composition [Si] / [C] is 0.
When it is less than 15, it can be seen that the change of the adhesive force with time is large and the contamination of the adherend is advanced. However, no silicone contamination was observed, and it is clear that the contamination was due to the acrylic pressure-sensitive adhesive.

Production Examples 3 to 10 67 g of toluene was charged into the reactor used in Production Example 1, heated to 75 ° C. while blowing nitrogen gas, and a mixed solution having the composition shown in Table 2 was charged over 2 hours. The reaction was continued for another 5 hours at the same temperature, then heated to 85 ° C. and reacted for 4 hours to synthesize a polysiloxane group-containing polymer. Toluene was added to the obtained polymer solution to prepare a 20 wt% solution. The content of the polymer component in the polymer solution after completion of the reaction is also shown in Table 2.

Examples 3 to 10 and Comparative Example 6 By the same method as in Example 1, 3 parts by weight of the polymer synthesized in Production Examples 3 to 10 was mixed with 100 parts by weight of the resin component of the pressure-sensitive adhesive A, and then an adhesive film was prepared. Created. As an adherend, an aluminum plate (A1100, manufactured by Nippon Test Panel) and a polycarbonate plate (manufactured by Mitsubishi Gas Chemical Co., Inc., Iupilon) were used to measure the change with time of the adhesive force in the same manner as in Example 1. In addition, in order to indirectly know the degree of silicone contamination of the adherend, a 2.5 cm wide adhesive tape manufactured by Sekisui Chemical Co., Ltd. is attached to the surface of the adherend after peeling the adhesive film from the adherend. Under the same conditions as when the pressure-sensitive adhesive film prepared above was applied, the 180 ° peeling force was measured after standing for 2 hours. 180 for adhesive tape than before sticking adhesive film
The smaller the peel strength, the more the adherend was contaminated with silicone. Table 3 shows the measurement results. In addition, as a comparison, measurement was carried out when 3 parts of the polydimersiloxane used in Comparative Example 4 was blended. The 180 ° peeling force of Sekisui Chemical Cellotape on the aluminum plate and the 180 ° peeling force on the polycarbonate plate were 510 g / cm before sticking the adhesive film.

From the results in Table 3, it was shown that even if the adherend was an aluminum plate or a polycarbonate plate, the adhesive force of the adhesive film prepared from the adhesive composition of the present invention did not change with time. Further, the result of measuring the 180 ° peeling force of Cellotape on the adherend after peeling the adhesive film showed that silicone contamination hardly occurred.

Production Examples 11 to 15 (A) Synthesis of peroxy bond-containing group polymer 400 parts of toluene was charged in the same reactor as in Production Example 1,
It is heated to 70 ° C while blowing nitrogen gas into it, and toluene is 170 parts, methyl methacrylate is 280 parts, 2-ethylhexyl acrylate is 80 parts, and 2-hydroxyethyl methacrylate is 40 parts. The mixed liquid consisting of was prepared over 2 hours, and the polymerization reaction was further carried out for 4 hours. The polymerization conversion was 96%, and the number average molecular weight of the obtained polymer was 13,000.

(B) Synthesis of block copolymer 50 parts of the polymer solution synthesized in (A) above was charged into the same reactor as above, and a mixture having the composition shown in Table 4 was added at 70 ° C for 30 minutes while blowing nitrogen gas. Prepared, and then 70 ℃
Polymerization was carried out for 3 hours at 80 ° C. for 3 hours. The solid content concentration after completion of the polymerization is shown in Table 4. The polysiloxane used had a number average molecular weight of 10,000 and had the following structure.

Polysiloxane 1 Next, the unreacted polysiloxane was extracted by the same operation as in Production Example 1. The polysiloxane content of the polysiloxane group-containing polymer portion was determined from the residual amounts of methyl methacrylate and butyl methacrylate and the amount of extracted polysiloxane analyzed by GC.

Table 4 shows the results. The polymer after removal of unreacted polysiloxane was dissolved in toluene to prepare a 20 wt% solution.

Examples 11 to 13 and Comparative Examples 7 to 8 Instead of the pressure sensitive adhesive A, 2-ethylhexyl acrylate / butyl methacrylate / acrylic acid (preparation composition: 85 /
(10/5 weight ratio) 2 parts by weight of the polymer synthesized in Production Examples 11 to 15 with a pressure-sensitive adhesive comprising a copolymer (solid content concentration: 40%, solvent: toluene) per 100 parts of resin content. Except for the above, the change with time in adhesive strength and the degree of contamination of the adherend were measured in the same manner as in Example 4. The results are shown in Table 5.

From the results shown in Table 5, it was found that the pressure-sensitive adhesive film prepared from the pressure-sensitive adhesive composition of the present invention showed little change in adhesive force with time and almost no contamination of the adherend with silicone. As is clear from Comparative Example 7, when the polysiloxane group content of the polysiloxane group-containing polymer portion in the block copolymer was 3.3% less, surface activity did not occur and the effect was insufficient. Further, as shown in Comparative Example 8, the polysiloxane group content in the polysiloxane group-containing polymer portion was 88%.
Even if it is too high, the [Si] / [C] on the surface of the adhesive film is 0.
It was not as large as 14 and was not sufficient as an effect of suppressing the change with time of the adhesive strength.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Yoshiyuki Yanagida, 13-13 Higashi Nara, Ibaraki City, Osaka Prefecture (56) References JP-A-63-291972 (JP, A) JP-A-63-291969 (JP, A)

Claims (5)

(57) [Claims] 1. A mixture of one or more polysiloxane group-containing compounds selected from the group represented by the following general formulas (I) to (II) in 100 parts by weight of an acrylic pressure-sensitive adhesive. Polysiloxane group-containing copolymer, which is a graft copolymer of methacrylic acid, methacrylic acid ester, acrylic acid, acrylic acid ester, acrylic acid ester, and fatty acid vinyl ester, with one or a mixture of two or more monomers selected from the group consisting of A polymer that does not contain a polysiloxane group, which is a polymer of the united portion and one or more polymers selected from the group consisting of methacrylic acid, methacrylic acid ester, acrylic acid, acrylic acid ester, and fatty acid vinyl ester. Emission of photoelectrons from the surface of the pressure-sensitive adhesive layer on the surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film containing 0.1 to 10 parts by weight of a block copolymer consisting of A peelable pressure-sensitive adhesive composition, characterized in that the molar ratio of silicon atoms to carbon atoms measured by an X-ray photoelectron analyzer under the condition of an angle of 90 degrees is in the range of 0.15 to 0.45. (In the formula, R ₁ is a hydrogen atom or a methyl group, R ₂ is a methyl group,
Ethyl group, phenyl group or Are shown, R ₅ is a hydrogen atom, a phenyl group or _{C p H 2p + 1, R} 6
Represents a methyl group, an ethyl group represents a phenyl group, and m
Is an integer of 1 or more, p represents an integer of 1 to 10, R ₃ is a hydrogen atom, a phenyl group or _{C p H 2p + 1, R} 4 represents a methyl group, an ethyl group or a phenyl group, respectively, n represents An integer greater than or equal to 1,
p is an integer of 1-10. ] 2. A polysiloxane group-containing compound selected from the group represented by the following general formulas (I) and (II) in combination or (II) alone in 100 parts by weight of an acrylic pressure-sensitive adhesive. Graft copolymerization of one or a mixture of two or more thereof with one or a mixture of two or more monomers selected from the group consisting of methacrylic acid, methacrylic acid ester, acrylic acid, acrylic acid ester and fatty acid vinyl ester. X, which contained 0.1 to 10 parts by weight of the polysiloxane group-containing copolymer as a unit, and was measured under the condition that the escape angle of photoelectrons from the surface of the pressure-sensitive adhesive layer was 90 degrees on the surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film.
A peelable pressure-sensitive adhesive composition, characterized in that the molar ratio of silicon atoms to carbon atoms measured by a line photoelectron analyzer is in the range of 0.15 to 0.45. (In the formula, R ₁ is a hydrogen atom or a methyl group, R ₂ is a methyl group,
Ethyl group, phenyl group or Are shown, R ₅ is a hydrogen atom, a phenyl group or _{C p H 2p + 1, R} 6
Represents a methyl group, an ethyl group represents a phenyl group, and m
Is an integer of 1 or more, p represents an integer of 1 to 10, R ₃ is a hydrogen atom, a phenyl group or _{C p H 2p + 1, R} 4 represents a methyl group, an ethyl group or a phenyl group, respectively, n represents An integer greater than or equal to 1,
p is an integer of 1-10. ] 3. The graft copolymer according to the general formula (I)
A mixture of one or more compounds containing a polysiloxane group represented by the formula (1), a mixture of one or more compounds containing a polysiloxane group represented by the general formula (II), methacrylic acid, methacrylic acid The peelable pressure-sensitive adhesive according to claim 1 or 2, which is a graft copolymer with one or a mixture of two or more monomers selected from the group consisting of acid esters, acrylic acid, acrylic acid esters and fatty acid vinyl esters. Composition. 4. In the polysiloxane group-containing copolymer,
One or two of the compounds represented by the general formulas (I) to (II)
Containing 5 to 85% by weight of a constitutional unit based on a mixture of one or more kinds, and one or more kinds of monomers selected from the group consisting of methacrylic acid, methacrylic acid ester, acrylic acid, acrylic acid ester and fatty acid vinyl ester. The peelable pressure-sensitive adhesive composition according to claim 1, 2 or 3, which comprises 15 to 95% by weight of the structural unit based on. 5. A polysiloxane group-containing copolymer comprising 5 to 85% by weight of one or more polysiloxane group-containing compounds represented by the general formula (II), methacrylic acid, methacrylic acid ester, and acrylic acid. The peelable adhesive according to claim 1 or 2, which is a graft copolymer with 15 to 95% by weight of one or a mixture of two or more monomers selected from the group consisting of acids, acrylic acid esters and fatty acid vinyl esters. Agent composition.