JPH09263747A - Adhesive resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adhesive resin compsn. excellent in high-temp. adhesive properties and low-temp. peelability by compounding a specific (meth)acrylic ester prepolymer and an aliph. linear isocyanate. SOLUTION: An adhesive resin compsn. useful for producing a self-adhesive, an adhesive, a coating material, etc., is obtad. by compounding, as the essential ingredients, a prepolymer having a wt. average mol.wt. of 100,000-1,500,000 and an aliph. linear isocyanate having, on average, two isocyanate groups in the molecule. At least 50wt.% of structural units of the prepolymer are derived from a (meth)acrylic ester represented by the formula (where in R is H or CH3 ; and (n) is 8 or higher) (e.g. hexadecyl acrylate); and at least 0.1wt.%, from a (meth)acrylic ester having at least one active hydrogen atom (e.g. hydroxyethyl acrylate).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curable adhesive resin composition containing a side chain crystalline polymer as a main component, which is used for pressure sensitive adhesives, adhesives, insulating coatings, paints and the like.

[0002]

2. Description of the Related Art An adhesive film for surface protection is attached to a substrate such as a stainless steel plate or a color steel plate, is subjected to processing such as bending, drawing and cutting, and is then peeled and removed. The number of cases in which adhesive films are also used for surface protection during processing and molding of electronic parts for semiconductors and liquid crystals has increased. These electronic components have become thinner and smaller year by year, and along with this, the adhesive film has functions such as light peelability that does not damage the adherend when peeling, and automatic peelability that can correspond to mass production. It is becoming more demanding.

A UV light release type adhesive film used for dicing a silicone wafer for semiconductors is an adhesive film using radiation curing type adhesiveness, and is irradiated with radiation such as UV to release the adhesive when used as a tertiary adhesive. This is a method in which the adhesive force is reduced by the original cross-linking to easily peel off. There is also a method of using a pressure-sensitive adhesive film using a heat-foaming type pressure-sensitive adhesive, and heating at the time of peeling to foam the pressure-sensitive adhesive to reduce the adhesive area with the metal foil and peeling. On the other hand, in the case of a temperature activated adhesive film using an adhesive whose adhesive strength changes drastically before and after the switching temperature, an acrylic polymer having a side chain having crystallinity has been used as its main component. Further, as a cross-linking agent for improving the cohesive force of the polymer, an average of 3 in one molecule based on the aromatic skeleton is used.
Isocyanates with one or more functional groups have been used.

[0004]

However, the UV light release type adhesive film requires a radiation irradiation device,
It was necessary to pay attention to storage and process control such that the adhesive strength after irradiation was likely to vary, the base film was refrigerated, and peeled from natural light. Further, in the heat-foamable pressure-sensitive adhesive film, a high temperature of 100 ° C. or higher was required for its foaming. Furthermore, any adhesive film was expensive as compared with a general-purpose adhesive film.

On the other hand, the temperature-activatable pressure-sensitive adhesive film has almost no above-mentioned drawbacks, and has characteristics such as dynamic adhesive strength change and reusability as compared with the UV light release type pressure-sensitive adhesive film. However, once the pressure-sensitive adhesive is cross-linked with a cross-linking agent such as aromatic trifunctional isocyanate for the purpose of imparting cohesive force, the dynamic property of change in adhesive force, particularly the adhesive force at high temperature, is impaired. There was a drawback that it would end up.

The present invention has been made in view of the above circumstances, and has a good dynamic of the change in adhesive force, particularly good adhesiveness at high temperature and good releasability at low temperature, and has extremely high contamination of the adherend surface after peeling. It is an object to provide a low level adhesive composition.

[0007]

According to the present invention, such an object is achieved by an adhesive resin composition containing the following (1) and (2) as essential components. (1) 50 wt% or more of the unit monomer constituting the polymer is composed of (meth) acrylic acid ester of n ≧ 8 in the following structural formula, and 0.1 wt% or more of the unit monomer constituting the polymer is one molecule. having at least one active hydrogen (meth) prepolymer CH ₂ = CRCOO- (CH ₂₎ having a weight average molecular weight of the acrylic acid ester is in the range of 100000 to 1500000 _n -H (R is H or during CH ₃ ) (2) Linear aliphatic isocyanate having an average of 2 isocyanate groups in one molecule Hereinafter, the present invention will be described in detail.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A (meth) acrylic acid ester of n ≧ 8 in the following structural formula, which is a main component in the present invention, means octyl (meth) acrylate (n =
8), decyl (meth) acrylate (n = 10), dodecyl (meth) acrylate (n = 12), tetradecyl (meth) acrylate (n = 14), hexadecyl (meth) acrylate (n = 16), octadecyl (meth) )
Acrylate (n = 18), Icosyl (meth) acrylate (n = 20), Docosyl (meth) acrylate (n
= 22), etc., but the composition exhibits particularly suitable temperature activity when n = 14, n = 16, n = 18, n =
It's 22. These unit monomers are required to account for 50 wt% or more of the total monomers constituting the polymer, and below this, the composition shows no or almost no temperature activity. _{CH 2 = CRCOO- (CH 2)} n -H (R is H or CH ₃₎

On the other hand, a (meth) acrylic acid ester having at least one active hydrogen in one molecule means (meth)
Acrylic acid, hydroxyethyl (meth) acrylate,
Examples include ethoxyethyl acrylate, (meth) acrylamide, diacetonoacrylamide, N-methylol (meth) acrylamide, dimethylaminoethyl (meth) acrylate, and N-vinylpyrrolidone.
(Meth) acrylic acid, hydroxyethyl (meth) acrylate, and (meth) acrylamide have excellent reactivity with isocyanate. In order for these unit monomers to crosslink and have an appropriate cohesive force, the proportion of the (meth) acrylic acid ester monomer having at least one active hydrogen atom in one molecule of all the monomers constituting the polymer is
0.1 wt% or more is required.

As the polymer-constituting monomers other than the above-mentioned two types, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-
In addition to (meth) acrylic acid esters such as ethylhexyl (meth) acrylate, vinyl acetate, vinyl chloride, and other vinyl monomers may be used, or epoxy acrylate, urethane acrylate, polyether acrylate, polyester acrylate, etc. may be copolymerized. You can also In particular, epoxy acrylate and polyether acrylate are excellent in terms of adhesiveness, and as the epoxy acrylate, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, acrylic alcohol diglycidyl ether, and resorcinol diglycidyl ether are used. , Adipic acid diglycidyl ester, phthalic acid diglycidyl ester, polyethylene glycol diglycidyl ether having an addition mole number of 5 or less, trimethylolpropane tridiglycidyl ether, glycerin triglycidyl ether, pentaerythritol tetraglycidyl ether, sorbitol tetraglycidyl ether, etc. (Meth) acrylic acid adduct of Since epoxy acrylate has a hydroxyl group in the molecule, it is considered that it contributes to the improvement of adhesiveness. These acrylic monomers may be used in combination of two or more, if necessary.

The weight average molecular weight of the prepolymer can be adjusted by the concentration of the initiator, the concentration of the chain transfer agent such as a mercapto compound, or the concentration of the monomer, and is selected from the range of 100,000 to 1,500,000. When the molecular weight is 100,000 or less, the cohesive force of the composition is too low, and thus the composition may be transferred to an adherend. Further, if the molecular weight is 1.5 million or more, the viscosity becomes too high, which makes handling very difficult.

The second essential component of the present invention, which is a linear aliphatic isocyanate having an average of two isocyanate groups in one molecule, is hexamethylene diisocyanate, trimethylhexamethylene diisocyanate or polyethylene glycol. Examples thereof include a dihexamethylene diisocyanate addition condensate, a trimethylhexamethylene diisocyanate addition condensate, a polypropylene glycol dihexamethylene diisocyanate addition condensate, and a trimethylhexamethylene diisocyanate addition condensate. These may be used alone or as a mixture of two or more. The addition amount of these cross-linking agents is 0.
It may be selected in the range of 1 to 50 parts by weight, preferably 1 to 30 parts by weight. If this amount is less than 0.1 part by weight, curing will be insufficient, and if it exceeds 50 parts by weight, excessive crosslinking will occur, which may adversely affect the adhesiveness.

If necessary, the adhesive resin composition used in the present invention may contain additives such as a diluent, a plasticizer, an antioxidant, a filler and a tackifier. The composition according to the present invention can be applied to a plastic film such as PE, PP, or PET, and subjected to a solvent-drying / heat-curing step to form a tape.

The reason why the effects of the present invention are exhibited is not clear, but it is presumed as follows. That is, n ≧
The prepolymer containing the straight-chain alkyl acrylate monomer of No. 8 as the main component has crystallinity in the side chain, and thus physical properties including mechanical properties change drastically around the melting point. As a result, regarding the adhesiveness, the polymer has a minimum at the melting point in the crystalline state or lower, and a maximum in the amorphous state above the melting point. on the other hand,
When this crystalline polymer is cross-linked with a cross-linking agent having a rigid skeleton or a polyfunctional cross-linking agent having three or more functional groups, the crystallinity may be impaired or a great amount of time may be required for crystallization due to the reduced mobility due to the cross-linking. Become. However, if a bifunctional linear aliphatic isocyanate is used as a cross-linking agent,
It is considered that the reduction in mobility is minimized and the dynamics of the adhesive force around the melting point are maintained.

[0015]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Synthesis of Prepolymer Hexadecyl acrylate (hereinafter abbreviated as C ₁₆ A), ethyl acrylate (hereinafter abbreviated as EA) and 2-hydroxyl ethyl acrylate (hereinafter abbreviated as HEA)
Azobisisobutyronitrile (hereinafter abbreviated as AIBN) was used as a polymerization initiator, and ethyl acetate (hereinafter abbreviated as EtAc) was used as a solvent in a nitrogen stream for 4 hours for polymerization to obtain an acrylic prepolymer. It was For the purpose of removing residual monomers and low molecular weight substances, the prepolymer solution was thoroughly stirred and washed in about 10 volumes of ethyl alcohol. The precipitated acrylic prepolymer was isolated and dried in a vacuum dryer at 80 ° C. for 12 hours. Then, the prepolymer was dissolved and diluted in toluene so that the solid content concentration was 20% by weight. It was synthesized by using octadecyl acrylate (hereinafter abbreviated as C ₁₈ A) and docosyl acrylate (hereinafter abbreviated as C ₂₂ A) in the same manner as C ₁₆ A.
In addition, butyl acrylate (hereinafter, abbreviated as BA) and acrylic acid (hereinafter, A
A polymer using (A) was also synthesized. Table 1 shows the charged amount of each acrylic ester, the weight average molecular weight of the obtained prepolymer, and the melting point. In addition, in Table 1, the molecular weight is GPC (gel permeation chromatography).
Is the polystyrene-converted weight average molecular weight, and the melting point is the value measured by DSC (differential scanning calorimeter) (10 ° C./min)
It is. To 100 parts by weight of the obtained prepolymer, various isocyanates (HMDI: hexamethylene diisocyanate, TMDI: trimethylhexamethylene diisocyanate, TDI: tolylene diisocyanate, trimethylolpropane triisocyanate and coronate L: manufactured by Nippon Polyurethane Industry Co., Ltd.) 5 -10 parts by weight were added and mixed. These compositions were uniformly applied to a 60 μm-thick polyethylene film so that the thickness after drying was 10 μm, and dried at 80 ° C. for 20 minutes to obtain a pressure-sensitive adhesive sheet. The obtained pressure-sensitive adhesive sheet was placed on a stainless steel plate (SUS430BA) of 100 μm, and the temperature was 10 ° C. higher than the melting point.
It was attached at a high temperature of 6 kgf / cm and 2 m / min. Then, the stainless steel plate was peeled off at a melting point of the adhesive film or higher (melting point + 10 ° C.) and a melting point or lower (melting point −10 ° C.) to measure the adhesive strength. At the same time, the surface condition of the adherend was visually observed. The results are summarized in Table 1.

Examples 1 to 8 have all the constituent requirements of the invention, and all satisfy the required characteristics.
In Comparative Examples 1 to 7 which are out of the constitutional requirements of the present invention, any of the required characteristics is lacking.

[0017]

[Table 1]

[0018]

As is clear from the examples, the adhesive resin composition according to the present invention has good adhesiveness at high temperature and good releasability at low temperature, and further has no stain on the surface of the adherend after peeling. It is an excellent temperature activated adhesive due to its extremely low level, and its industrial value is great.

Continuation of the front page (72) Inventor Yasushi Oyama 1150 Goshomiya, Shimodate City, Ibaraki Prefecture Hitachi Chemical Co., Ltd. Goshomiya Factory

Claims (5)

[Claims] 1. An adhesive resin composition comprising the following (1) and (2) as essential components. (1) 50 wt% or more of the unit monomer constituting the polymer is composed of (meth) acrylic acid ester of n ≧ 8 in the following structural formula, and 0.1 wt% or more of the unit monomer constituting the polymer is one molecule. having at least one active hydrogen (meth) prepolymer CH ₂ = CRCOO- (CH ₂₎ having a weight average molecular weight of the acrylic acid ester is in the range of 100000 to 1500000 _n -H (R is H or during CH ₃ ) (2) Linear aliphatic isocyanate having an average of 2 isocyanate groups in one molecule 2. The adhesive resin composition according to claim 1, wherein the prepolymer according to claim 1 (1) has a melting point of 0 to 60 ° C. 3. The adhesive resin composition according to claim 1, wherein the group having active hydrogen according to claim 1 (1) is a hydroxyl group or a carboxyl group. 4. The linear aliphatic isocyanate according to claim 1 (2) is hexamethylene diisocyanate or trimethylhexamethylene diisocyanate.
4. The adhesive resin composition according to any one of 3 to 3. 5. A composition obtained by coating an adhesive resin composition, which comprises the components according to claim 1 as an essential component, on a plastic film.