JP2003027036A - Adhesive composition for hot melt application - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adhesive composition for hot melt application that furnishes an effective adhesion force even when used for an adherend that is hard to bond owing to mirror-like lapping that allows little anchoring effect of an adhesive. SOLUTION: This adhesive composition for hot melt application comprises a polymer obtained by polymerizing monomer components having, as an indispensable component, a monomer with a carboxyl group in the molecule, a homopolymer therefrom having a glass transition temperature of <0 deg.C. Specifically, the polymer is an acrylic block polymer comprising 50-100 wt.% of a (meth)acrylate structural unit per the whole polymer. It is preferable that the acrylic block polymer is obtained by a multi-stage polymerization process in the presence of a multivalent mercaptan.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive composition for hot-melt coating, which has excellent adhesion to a mirror-finished adherend which is a difficult-to-adhere body and has an excellent balance of adhesive properties. Specifically, it relates to a pressure-sensitive adhesive composition intended for hot melt coating.

[0002]

2. Description of the Related Art A mirror-finished adherend is an adhesive tape,
28 specified in JIS-Z 0237, which is an industrial standard for sheets
It is an adherend that is more difficult to bond than an adherend that is polished with No. 0 water-resistant abrasive paper. The reason for this is not clear, but the surface roughness of the adherend that has been mirror-finished is about 0.05 micron, which is less than the surface roughness of the adherend that has been polished with No. 280 water-resistant abrasive paper. It is considered that the anchoring effect (anchor effect) of the pressure-sensitive adhesive is small due to the small size. As a method for improving the adhesiveness to such a mirror-like adherend which is a difficult-to-adhere body, as a pressure-sensitive adhesive composition, a monomer containing a polar group represented by a carboxyl group (for example, acrylic acid, methacrylic acid, etc. It is effective to use a polymer obtained by polymerizing the component).

Acrylic acid, which has been conventionally used as a method for improving the adhesion to a mirror-like adherend which is a difficult-to-adhere body,
Monomers containing carboxyl groups such as methacrylic acid
Although it is a pressure-sensitive adhesive using a polymer obtained by polymerizing using components, a pressure-sensitive adhesive containing a polymer obtained by increasing the amount of the monomer has an effect of improving the adhesion to an adherend. However, there was a problem that tack and adhesive strength were significantly reduced.

The reason why a polymer obtained by polymerizing a monomer component containing a carboxyl group such as acrylic acid or methacrylic acid reduces tack is as follows.
That the carboxyl group is easily oriented on the surface of the adhesive,
Then, it is considered that the homopolymer of the monomer containing these carboxyl groups has a high glass transition point.

In particular, in a pressure-sensitive adhesive composition for hot melt coating, the tack described above is often difficult to develop depending on the form of use, and normally hot melt coating using a polymer by these methods is used. In the adhesive for industrial use, it is difficult to obtain an adhesive that adheres to an adherend, and that satisfies tack and adhesive strength as a pressure-sensitive adhesive composition for hot-melt coating, and it is difficult to obtain an adhesive composition for hot-melt coating. In that case, there is still room for studying the form of the polymer to be used, in addition to studying the components to be added such as additives.

[0006]

The object of the present invention is to provide good adhesion to, for example, a mirror-like adherend which is a difficult-to-adhere body, that is, an adherend having a small anchoring effect (anchor effect) of an adhesive. It is also an object of the present invention to provide a new type of pressure-sensitive adhesive composition for hot melt coating, which can sufficiently exhibit tack and tackiness.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have adopted a polymer using a specific monomer component as a polymer component of an adhesive for hot melt coating. did. Specifically, by using a polymer obtained by polymerizing using a monomer having a carboxyl group in the molecule and having a glass transition point of a homopolymer lower than 0 ° C., and preferably, The above object is achieved by using an acrylic block polymer obtained by polymerizing using a monomer having a carboxyl group in the molecule and having a homopolymer having a glass transition point of less than 0 ° C. The present invention has been accomplished by finding that it can be used as an adhesive for hot melt coating.

Specifically, the constitution of the present invention is obtained by polymerizing a monomer component containing a monomer having a carboxyl group in the molecule and having a homopolymer having a glass transition point of less than 0 ° C. as an essential component. It is a pressure-sensitive adhesive composition for hot melt coating containing a polymer to be obtained. More specifically, it is a pressure-sensitive adhesive composition for hot melt coating, wherein the polymer is an acrylic block polymer containing 50 to 100% by weight of a (meth) acrylic acid ester structural unit. Further, the acrylic block polymer is a polymer obtained by a multi-step polymerization step in the presence of a polyvalent mercaptan, and the acrylic block polymer, at least the first step in the multi-step polymerization step It is a preferred embodiment of the present invention that the polymer is obtained by performing a multi-stage polymerization process in which monomer components having different compositions are used in the second-stage polymerization process. Furthermore, a pressure-sensitive adhesive composition for hot-melt coating, wherein the acrylic block polymer is a star-shaped block polymer having a plurality of polymer chains extending from polyvalent mercaptan, is a preferred embodiment of the present invention.

For example, as an example of the pressure-sensitive adhesive composition used in the present invention, a copolymer having a carboxyl group in the molecule and a homopolymer having a glass transition point of less than 0 ° C. No. 5-112764, a radical-polymerizable monomer having a Tg of a homopolymer of -20 ° C or less for the purpose of providing a pressure-sensitive adhesive which is easily dissolved in an alkaline aqueous solution and has excellent water resistance and pressure-sensitive adhesive properties is 10 to 70. There is a description of an adhesive containing wt%.

Further, Japanese Patent No. 2627719 discloses that 2-hydroxyethyl (meth) acrylate contains ε-caprolactone or δ-valerolactone for the purpose of improving cohesive force at high temperature and solvent resistance to polar solvents. There is a disclosure of a pressure sensitive adhesive composition containing 0.1 to 8% by weight of an added polymerizable monomer.

In all of the above patents, the homopolymers having a carboxyl group in the molecule and having a glass transition point of less than 0 ° C. were used for polymerization in the present invention. Although a pressure-sensitive adhesive composition composed of a polymer is described, no description of a pressure-sensitive adhesive composition intended for hot melt coating is made, and the adhesive properties of the disclosed pressure-sensitive adhesive composition are described. However, it does not have excellent adhesion to a mirror-finished adherend, which is the object of our intention, which is a difficult-to-adhere body, and does not have an excellent balance of adhesive properties when used as an adhesive.

Further, there is no description about the acrylic block polymer obtained by the multi-step polymerization process in the presence of polyvalent mercaptan, which is the constitution of the polymer form adopted by us. In addition, it has excellent physical properties as an adhesive for hot-melt coating, excellent adhesion to mirror-finished adherends that are difficult to adhere to, and an excellent balance of adhesive properties when used as an adhesive for hot-melt coating. Is not suggested at all.

The present invention will be described in more detail below.

In the pressure-sensitive adhesive composition for hot melt coating of the present invention, the amount of the monomer having a carboxyl group in the molecule and having a homopolymer having a glass transition point of less than 0 ° C. is It is preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, based on the total amount of all the monomers used for obtaining the coalescence. If the amount of the monomer used is less than 1% by weight, the adhesion to the mirror-like adherend when used as an adhesive will be poor, and if it exceeds 20% by weight, tack will decrease. In addition, the hot melt coatability may decrease.

Specific examples of such a monomer having a carboxyl group in the molecule and having a glass transition point of a homopolymer lower than 0 ° C. include, for example, monohydroxyethyl (meth) acrylate succinate; or A compound represented by the following general formula (1) obtained by adding one or more ε-caprolactone to (meth) acrylic acid:

[0016]

[Chemical 1]

(In the above formula, R represents a hydrogen atom or a methyl group, and n represents an integer of 1 or more.) Alternatively, it can be obtained by adding one or more ε-caprolactone to 2-hydroxyethyl (meth) acrylate. A compound represented by the following general formula (2):

[Chemical 2]

(Wherein R represents a hydrogen atom or a methyl group, and n represents an integer of 1 or more), or polyethylene glycol mono (meth) acrylate or polypropylene glycol mono (meth) acrylate. , A compound obtained by reacting an acid anhydride; and the like, and they can be used in any combination.

In the pressure-sensitive adhesive composition of the present invention, in order to obtain the polymer, a homopolymer having a carboxyl group in the molecule, represented by (meth) acrylic acid, has a glass transition point of 0. It is also possible to use a monomer having a temperature of ℃ or more in combination. In that case, the amount used is preferably 5% by weight or less. If it exceeds 5% by weight, tack will decrease.

In the embodiment of the acrylic block polymer of the present invention, a homopolymer having a carboxyl group in the molecule, represented by (meth) acrylic acid, has a glass transition point of 0 ° C. or higher. An acrylic block polymer obtained by polymerizing a monomer and a monomer component having both a carboxyl group in the molecule and a homopolymer having a glass transition point of less than 0 ° C. as essential components is also preferable. one of. As described above, by using the monomers having two kinds of carboxyl groups having different glass transition temperatures of the homopolymer in combination, it is possible to improve the adhesive property of the resulting acrylic block polymer and the adhesion to the substrate. You can

As the other polymerizable monomer used in the present invention, any monomer can be used as long as it can form a homopolymer or a copolymer by radical polymerization.
Can also be used.

For example, alkyl (meth) acrylate having 1 to 30 carbon atoms, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate,
Glycidyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate
(Meth) acrylates typified by styrene, ethoxyethoxyethyl (meth) acrylate, etc .; styrene-based monomers typified by α-methylstyrene, vinyltoluene, styrene, etc .; phenylmaleimide, cyclohexylmaleimide Maleimide monomers represented by the following; vinyl ether monomers represented by methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether, etc .; fumaric acid, fumaric acid monoalkyl ester, fumaric acid Dialkyl ester; maleic acid, monoalkyl ester of maleic acid, dialkyl ester of maleic acid; itaconic acid, monoalkyl ester of itaconic acid,
Dialkyl ester of itaconic acid; (meth) acrylonitrile, butadiene, isoprene, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl ketone, vinyl pyridine, vinyl carbazole, etc., and any one of them may be used alone, or two or more of them may be used. Can be used together.

In the acrylic block polymer of the present invention, the preferred composition of each polymer portion obtained in the multi-step polymerization step is a polymer portion having a glass transition point of 0 ° C. or more and a polymer portion having a glass transition point of less than 0 ° C. It is a combination of polymer portions having a glass transition point.

The glass transition point of the polymer portion mentioned here is a value calculated using the Fox equation represented by the following equation.

[0025]

[Chemical 3]

Block polymers generally composed of a combination of polymer portions having different glass transition points are known to have a microphase-separated structure, and polymer portions having a high glass transition point form a discontinuous phase. Since it has a pseudo-crosslinked structure, it has higher cohesive force than conventional adhesives,
Excellent heat resistance. On the other hand, the polymer portion having a low glass transition point forms a continuous phase and exhibits tackiness. In this case, the lower the glass transition point, the greater the effect of increasing the tackiness.

The acrylic block polymer used in the present invention is not particularly limited in its production method as long as it has a polymer portion at 0 ° C. or higher and a polymer portion at less than 0 ° C. in one molecule. Not done.

As a method for producing such an acrylic block polymer, for example, a block polymer synthesized by living anionic polymerization, a block polymer obtained by living radical polymerization with an initiator, or a macromonomer. Examples thereof include a block polymer obtained by copolymerizing the above, a star block polymer synthesized by radical polymerization in the presence of a polyvalent mercaptan described later, and the like. The physical properties of the resulting polymer, the simplicity of the polymerization step, the manufacturing cost, in view of hot melt coating properties, the star block polymer synthesized by radical polymerization in the presence of polyvalent mercaptan is a preferred embodiment of the present invention. is there.

In the presence of the polyvalent mercaptan in the present invention, a star block polymer obtained by carrying out a plurality of stages of radical polymerization using different types of polymerizable monomers at each stage is used as follows. Polyvalent mercaptan can be used.

Examples of the polyvalent mercaptan include ethylene glycol dithioglycolate and ethylene glycol.
Rudithiopropionate, 1,4-butanediol dithioglycolate, 1,4-butanediol Dithiopropionate, etc. Diol and carboxyl such as ethylene glycol and 1,4-butanediol Group-containing mercaptans diesters; trimethylolpropane trithioglycolate, trimethylolpropane trithiopropionate and other triols such as trimethylolpropane, and triesters of carboxyl group-containing mercaptans;
Pentaerythritol tetrakisthioglycolate, pentaerythritol tetrakisthiopropionate and other compounds having four hydroxyl groups such as pentaerythritol and polyesters of mercaptans containing carboxyl groups; dipentaeryth Lithol hexakisthioglycollate
A compound having 6 hydroxyl groups such as dipentaerythritol, dipentaerythritol hexakisthiopropionate and a polyester compound of a carboxyl group-containing mercaptan; and a compound having 3 or more hydroxyl groups Polyester compound of carboxyl group-containing mercaptans; compound having three or more mercapto groups such as trithioglycerin; 2-di-n-butylamino-4,6
-Triazine polyvalent thio-, such as dimercapto-S-triazine and 2,4,6-trimercapto-S-triazine
Compounds; compounds obtained by adding hydrogen sulfide to a plurality of epoxy groups of a polyvalent epoxy compound to introduce a plurality of mercapto groups; esters obtained by esterifying a plurality of carboxyl groups of a polyvalent carboxylic acid with mercaptoethanol Compounds may be mentioned, either of which alone or
Two or more can be used together. Here, the carboxyl group-containing mercaptans include thioglycolic acid, mercaptopropionic acid, thiosalicylic acid, and the like.
It is a compound having one mercapto group and one carboxyl group.

In the case of synthesizing a block polymer using polyvalent mercaptan, a radical polymerization initiator usually used for polymerization [eg, 2,2'-azobisisobutyronitrile, 2,
Azo initiators such as 2′-azobis (2-methylbutyronitrile); peroxide polymerization initiators such as benzoyl peroxide, etc. can be used, but the weight ratio is usually 1/100 of that of polyvalent mercaptan. It is 3 or less, preferably 1/5 or less.
When the polymerization ratio is used in a larger amount than the above ratio, in addition to the polymer portion extended from the polyvalent mercaptan which gives the block polymer, a large amount of the polymer extended from the polymerization initiator is produced,
The production efficiency of the block polymer is lowered, and the physical properties of the obtained polymer are also lowered.

In the present invention, the radical polymerization can be carried out by ordinary radical polymerization such as bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization. The polymerization temperature is 30
-200 degreeC is preferable, More preferably, it is 50-150 degreeC.
Is.

One of preferred production methods for obtaining the acrylic polymer of the present invention will be described below. The acrylic block polymer of the present invention is obtained by a multi-step polymerization step in the presence of a polyvalent mercaptan, and monomers having different compositions from each other in at least the first step and the second step of the multi-step polymerization step. It is preferably obtained by carrying out a multi-step polymerization process using components.

That is, a star-shaped block polymer obtained by carrying out a plurality of stages of radical polymerization using different types of polymerizable monomers in each stage in the presence of polyvalent mercaptan is one of the preferable production modes. Is one.

By adopting this production method, the acrylic block polymer of the present invention becomes a star block polymer having a plurality of polymer chains extending from the polyvalent mercaptan, and exhibits good adhesive properties and tackiness. Although it has a sufficient weight average molecular weight to be able to be obtained, the melt viscosity at the time of heating can be set to be low by the above preferred embodiment, and as a result, good hot melt coatability can be achieved.
Therefore, the hot-melt coating pressure-sensitive adhesive containing the acrylic block polymer is a preferred embodiment of the present invention.

The production procedure is as follows: In the presence of polyvalent mercaptan, the first step is radical polymerization of the first polymerizable monomer component forming a polymer portion having a glass transition point of 0 ° C. or higher, Polymerization rate is 50% or more, preferably 60
% Or more, the second step is to add and polymerize a second polymerizable monomer component that forms a polymer portion having a glass transition point of less than 0 ° C. to give the block polymer of the present invention. Obtainable. The polymerization rate of the radical polymerization performed first is 50% or more because the properties of the polymer that forms the block even if the subsequent polymerization is performed without removing the polymerizable monomer remaining after the polymerization. Is to be as different as possible. Therefore, it is possible to volatilize and remove the polymerizable monomer after the first polymerization.

By repeating the above-mentioned polymerization step a plurality of times in multiple stages, a block polymer having three or more kinds of polymer block structures can be obtained.

In a preferred embodiment of the present invention, the monomer component containing as an essential component a monomer having a carboxyl group in the molecule and a homopolymer having a glass transition point of less than 0 ° C. is It may be contained in the polymerizable monomer component used in the first step, which is the polymerization step, or may be used in the second step. Considering from the viewpoint of improving the adhesion to the mirror-like adherend of the present invention, it is considered that it is more effective to use it in the second stage having a low glass transition point which will form a continuous phase. .

In the acrylic block polymer of the present invention, the preferred composition of each polymer part obtained in the multi-step polymerization step is a polymer part having a glass transition point of 0 ° C. or higher and a polymer part of less than 0 ° C. It is a combination of polymer portions having a glass transition point. The acrylic block polymer in the present invention is an acrylic block polymer obtained by polymerizing monomer components having different compositions in the first step and the second step of the multi-step polymerization step. Being coalesced is the preferred form.

More specifically, a monomer component having a calculated glass transition temperature of 0 ° C. or higher for the monomer component for the first polymer portion, which is used in the multi-step polymerization process, is used. And a monomer for which the calculated glass transition temperature of the monomer component for the second polymer portion is less than 0 ° C. It can be obtained by a multi-stage polymerization process including a second stage polymerization process in which the second polymer portion is obtained by polymerizing using the components.

The pressure-sensitive adhesive composition for hot melt coating of the present invention contains the above-mentioned acrylic block polymer of the present invention. The content of the acrylic block polymer is preferably 50 to 100% by weight when the pressure-sensitive adhesive composition for hot melt coating is 100% by weight. It is more preferably 60 to 100% by weight. More preferably, it is 70 to 100% by weight. If it is out of this range, good adhesive properties may not be obtained, or hot melt coatability may be deteriorated. Further, if necessary, a polymer other than the acrylic block polymer used in the present invention may be used in combination so as to have the above-mentioned blending to form a pressure-sensitive adhesive composition for hot melt coating.

The pressure-sensitive adhesive composition for hot melt coating according to the present invention may further contain other additives, if necessary. Examples of the additives include tackifiers such as rosin-based resins, terpene-based resins, aliphatic petroleum resins, aromatic petroleum resins, coumarone-indene resins, alkylphenol resins and xylene resins. Yes, one or more of them are used. The preferred amount of tackifier used is less than 100 parts by weight per 100 parts by weight of the acrylic polymer. Another additive is wax. Examples of the wax include natural wax, paraffin wax, polypropylene wax, polyethylene wax, and a (meth) acrylate polymer having a saturated alkyl group having 18 or more carbon atoms, and the like. More than one wax can be used. The preferred amount of the wax used is less than 100 parts by weight based on 100 parts by weight of the acrylic polymer. Other additives include, for example, compounds such as phthalates and adipates, which serve as plasticizers; fillers such as silica powder and titanium oxide; antioxidants such as dithiocarbamate and phenol compounds. It is at least one compound selected from Examples of the amount of these additives include the amounts conventionally used.

The pressure-sensitive adhesive composition for hot melt coating used in the present invention is melted into a liquid by heating, and it is a foil type hot melt applicator, a nozzle type hot melt applicator, or a hot type. Especially, if it is possible to coat with a melt roll coater, a hot melt extrusion coater, a hot melt slot orifice coater or the like which is generally used as a hot melt coater. No restrictions.

In summary, the adhesive composition for the purpose of hot melt coating, which comprises as an essential component a monomer of the present invention having a carboxyl group in the molecule and having a homopolymer having a glass transition point of less than 0 ° C. Since the carboxyl group in the polymer is oriented on the surface of the pressure-sensitive adhesive, the adhesion to the mirror-like adherend, which is a difficult-to-adhere body, is improved, and the glass transition point of the monomer is less than 0 ° C. Commonly used in (meta)
The remarkable tack found in the adhesive for hot melt coating, which is obtained by using a polymer having a carboxyl group and a homopolymer having a glass transition temperature of 0 ° C. or higher, such as acrylic acid, is used. It also has the feature of low deterioration. In summary, the hot-melt coating pressure-sensitive adhesive of the present invention has excellent adhesion to a mirror-finished adherend that is a difficult-to-adhere body,
Moreover, it has an excellent balance of adhesive properties. The hot melt coatability is also very good.

[0045]

EXAMPLES Examples of the present invention and comparative examples outside the scope of the present invention will be shown below, but the present invention is not limited to the following examples. In the following, "%" means "% by weight", "part"
Means "parts by weight". The number average molecular weight (M
n) and the weight average molecular weight (Mw) were calculated | required by the polystyrene conversion value by the gel permeation chromatography (GPC).

The properties as a hot melt adhesive were measured by the following methods. <Sample preparation> Hot melt adhesive is applied to GPD coater <
Yuri Roll Machine Co., Ltd.>, coating thickness 50 μm
A PET film was melt-coated so as to obtain a sample. <Voltack> J.S. Do
Measured at 23 ° C by w method, and stopped ball N
o. showed that. <Adhesive strength> The sample having a width of 25 mm was attached to a mirror-finished stainless steel (SUS) plate as an adherend, and JISZ-0 was used.
The 180 degree peel strength of 237 standard was measured. <Holding power> The sample was attached to a mirror-finished SUS plate with an adhesive area of 1/2 inch x 1 inch, and a load of 1 kg was applied at 23 ° C to measure the drop time. An example of producing a block polymer using polyvalent mercaptan is shown below, but the present invention is not limited to this example. <Viscosity at 180 ° C> The hot melt adhesive was heated to 180 ° C to melt it, and the melt viscosity was measured by a flow tester (manufactured by Shimadzu Corporation).

(Example 1-a) 2 liters of 4 equipped with a synthetic stirrer for the first polymer portion having a glass transition point of 0 ° C. or higher, a nitrogen introducing pipe, a dropping funnel, a thermometer, and a cooling pipe. As a first monomer, 295.5 g of methyl methacrylate, 4.5 g of tetraethylene glycol diacrylate and 280.9 g of ethyl acetate as a solvent were added to a one-necked flask, and the temperature was raised to 85 ° C. under a nitrogen atmosphere. . After the internal temperature reached 85 ° C, pentaerythritol tetrakisthioglycolate was obtained as polyvalent mercaptan.
10.5 g, radical polymerization initiator azobisisobutyronitrile 0.4 g, solvent ethyl acetate 30 g
Was charged to start the polymerization.

10 minutes after the initiation of polymerization, 689.5 g of methyl methacrylate and tetraethylene glycol diacryle
10.5 g, pentaerythritol tetrakisthioglycolate 24.5 g, azobisisobutyronitrile 0.8 g, and ethyl acetate 133.2 g were added dropwise over 110 minutes.

170 minutes after the start of the polymerization, the polymerization rate was 64.3%.
When the temperature reached, 0.1 g of methoxyphenol as a polymerization inhibitor and 592 g of ethyl acetate as a solvent were added, and the mixture was cooled to complete the first stage polymerization. (Example 1-b) Synthesis of a star-shaped block polymer using the first polymer portion A 2-liter four-necked flask equipped with a stirrer, a nitrogen inlet tube, a dropping funnel, a thermometer, and a cooling tube was placed. , 70.6 g of the polymer solution obtained in the above first step, butyl acrylate 1
51.7 g, 2-ethylhexyl acrylate 73.4
g, 4.9 g of acrylic acid, 14.7 g of monohydroxyethyl acrylate succinate and 282.7 g of ethyl acetate were added, and the temperature was raised to 85 ° C. under a nitrogen atmosphere. Inner temperature is 85
After reaching ℃, azobisisobutyronitrile 0.16
g and 24.5 g of ethyl acetate were added to initiate polymerization.

10 minutes after the start of the reaction, 131.0 g of the polymer solution obtained in the above first step and 28 butyl acrylate were added.
1.8 g, 2-ethylhexyl acrylate 136.3
g, 9.0 g of acrylic acid, 27.2 g of monohydroxyethyl acrylate succinate, 0.31 g of azobisisobutyronitrile, and 522.7 g of ethyl acetate were added dropwise over 200 minutes. 60 minutes, 90 minutes, and 120 minutes after the completion of the dropping, 0.2 g of azobisisobutyronitrile and 6.0 g of ethyl acetate were added, respectively, and the mixture was further reacted under reflux for 2 hours and then the polymerization was completed to obtain a solid content concentration of 44. A 9% polymer solution was obtained. (Post-treatment step) From the reaction solution thus obtained, volatile components such as ethyl acetate as a solvent and residual monomers are volatilized and removed by using a twin-screw extruder to obtain a star block polymer having 100% solids. It was

Table 2 shows the adhesive physical properties when the star block polymer obtained as described above was used as a hot melt adhesive. (Example 2) By the same operation as in Example 1, polymerization was carried out with the composition shown in Table 1 to obtain a star block polymer. In addition, the same post-treatment process and physical property measurement as in Example 1 were performed. The adhesive properties are shown in Table 2. (Comparative Examples 1 and 2) By the same operation as in Examples 1 and 2, polymerization was carried out with the composition shown in Table 1, and a star block polymer containing no monohydroxyethyl acrylate succinate as a monomer component. Got In addition, the same post-treatment steps and physical properties were measured as in Examples 1 and 2. The adhesive properties are shown in Table 2.

[0052]

[Table 1]

[0053]

[Table 2]

The holding force shown in Table 2 is a physical property value which usually indicates the cohesive force of the pressure-sensitive adhesive, and the state of failure of the pressure-sensitive adhesive when the sample falls is generally cohesive failure. However, when a mirror-finished SUS plate or the like is used as the adherend,
The pressure-sensitive adhesive itself may not be destroyed, but destruction at the interface between the pressure-sensitive adhesive and the adherend may occur, so-called interface destruction. This is considered to be a phenomenon that occurs because the adhesive force between the adhesive and the adherend that has been mirror-finished is inferior to the cohesive force of the adhesive.

When the acrylic acid of Examples 1 and 2 and monohydroxyethyl succinate acrylate were used together (the amount used was 4.85 × 10 ⁻⁴ mol / g), a large voltac and an adhesive force were obtained. It can be seen that, in addition, in the holding power measurement, no interfacial destruction with the adherend has occurred and the adhesiveness is good.

Meanwhile Comparative Example 1, a half amount of Examples 1 and 2 only acrylic acid ^- is a case where ^{(2.42 × 10 4 mol / g} ) used, good ball this case - shows the Rutakku value However, in the holding power measurement, it was found that the interface destruction occurred at 23 and 40 ° C. in a short time, and the adhesiveness with the mirror surface SUS was insufficient. In Comparative Example 2, only acrylic acid was used in the same amount as in Examples 1 and 2 (4.85 × 10 ⁻⁴ mol /
g) When used, in this case, the holding power at 23 and 40 ° C. does not cause interfacial destruction and the adhesion to the mirror surface SUS is good, but the volt-back is significantly reduced.

Therefore, a pressure-sensitive adhesive composition for hot melt coating using a polymer of the present invention, which is obtained by copolymerizing a monomer having a carboxyl group in the molecule and a homopolymer having a glass transition point of less than 0 ° C. Has the feature that both good adhesion to a mirror-finished adherend and good adhesive properties can be achieved.

Table 3 below shows the calculated Tg (glass transition temperature) of each polymer portion calculated according to the Fox equation of each portion of the polymers prepared in the above Examples and Comparative Examples.

[0059]

[Table 3]

[0060]

The novel pressure-sensitive adhesive composition for hot melt according to the present invention can have both excellent adhesion to a mirror-like adherend and excellent adhesive physical properties. Copolymerization of a monomer having a carboxyl group in the molecule of (meth) acrylic acid or the like and having a glass transition point of a homopolymer of 0 ° C. or higher, which is a general method for improving adhesion to a mirror-like adherend, Although the adhesiveness is improved as the amount thereof is increased, the glass transition point of the pressure-sensitive adhesive surface is improved, which causes adverse effects such as voltacks and reduction of the adhesive strength. On the other hand, in the copolymerization of a monomer having a carboxyl group in the molecule and having a glass transition point of a homopolymer of less than 0 ° C., which is used in the present invention, the glass transition point of the pressure-sensitive adhesive surface is Because it does not rise so much, it has excellent adhesive properties,
Moreover, the effect of improving the adhesion to the mirror-like adherend, which is derived from the carboxyl group, can be obtained.

The pressure-sensitive adhesive composition for hot melt coating of the present invention has a cohesive force and physical properties that can be practically used sufficiently, while having a low melt viscosity that enables hot melt coating. In particular, it becomes a pressure-sensitive adhesive for hot-melt coating which has an excellent balance between low melt viscosity that brings good workability and cohesive force in a room temperature to medium temperature use atmosphere, specifically, in use conditions of less than 80 ° C. . Further, since it does not contain a volatile component such as a solvent and water, it does not require a drying step, has high productivity, and has a cost merit. I can say. Further, in the case of the block polymer having a polymer portion at 0 ° C. or higher of the present invention, it is known that the polymer portion at 0 ° C. or higher acts as a pseudo-crosslinking point, and the cohesive force and physical properties at higher temperatures are improved. It becomes an excellent adhesive for hot melt coating.
Furthermore, when the polymer forming the pressure-sensitive adhesive for hot melt coating of the present invention is a star-shaped block polymer having a plurality of polymer chains extending from a polyvalent mercaptan, it directly has a branched structure. It has a low melt viscosity even with a high molecular weight as compared with a chain polymer, and can be a hot melt adhesive having excellent coatability.

Therefore, the use of the above polymer is
A preferred embodiment for obtaining a pressure-sensitive adhesive for hot-melt coating, which is one form of the present invention and has an excellent balance between a low melt viscosity that brings good workability and a cohesive force under use conditions of less than 80 ° C. Becomes

Claims (5)

[Claims] 1. A hot melt containing a polymer obtained by polymerizing a monomer component containing a monomer having a carboxyl group in the molecule and a homopolymer having a glass transition point of less than 0 ° C. as an essential component. Adhesive composition for coating. 2. The pressure-sensitive adhesive composition for hot melt coating according to claim 1, wherein the polymer is an acrylic block polymer containing 50 to 100% by weight of a (meth) acrylic acid ester structural unit. object. 3. The pressure-sensitive adhesive composition for hot-melt coating according to claim 2, wherein the polymer is an acrylic block polymer obtained by a multi-step polymerization process in the presence of polyvalent mercaptan. . 4. The polymer according to at least the first and second stages of the multi-stage polymerization process,
The pressure-sensitive adhesive composition for hot-melt coating according to claim 3, which is an acrylic block polymer obtained by carrying out a multi-step polymerization process using monomer components having different compositions from each other. 5. The hot melt coating according to claim 1, wherein the polymer is a star block polymer having a plurality of polymer chains extending from polyvalent mercaptan. Adhesive composition.