JPH07103187B2 - Method for producing styrene polymer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a styrene polymer, and more particularly to a method for producing a styrene polymer having a narrow molecular weight distribution useful as a tackifier resin.

Prior Art Adhesives are usually composed of a base polymer, a solid resin and a plasticizer. Examples of the base polymer include natural rubber, styrene-butadiene rubber, polyisobutylene, polychloroprene, block rubber and the like. The solid resin is a so-called tackifying resin, and has an action of imparting an appropriate wettability to the adhesive and adhering the adhesive to an adherend under a predetermined temperature, time and pressure. As the tackifying resin, aliphatic unhydrogenated petroleum resin, hydrogenated C5 petroleum resin,
Examples include hydrogenated C9 petroleum resin, stabilized rosin ester, and alkylstyrene polymer. Examples of the plasticizer include oils such as naphthenic oil and paraffinic oil, liquid rosin ester, and liquid hydrogenated petroleum resin.

The tackifying resin must have a desirable color tone (for example, colorless and transparent) and good compatibility with the base polymer together with the tackifying effect. This is because the quality of the color tone affects the appearance of the adhesive obtained, and if the compatibility with the base polymer is poor, the tack of the adhesive may decrease or phase separation may occur. is there.

By the way, the compatibility between the tackifying resin and the base polymer depends on the softening point of the tackifying resin, the polarities of the two, and the like.

When a pure monomer resin such as a styrene resin or an alkyl styrene resin (which usually has a high purity and a colorless color tone) is used as the tackifying resin, it is compatible as a base polymer. Considering that, a relatively polar polymer is used. For example, in the case of preparing an acrylic pressure-sensitive adhesive using a pure monomer resin and an acrylic copolymer, the content of a high molecular weight substance having a molecular weight of about 30,000 or more is usually found when the softening point of the pure monomer resin exceeds 100 ° C. Since the amount increases, the compatibility decreases. Further, when the softening point is less than 70 ° C, the compatibility is good, but the adhesive force and cohesive force of the obtained pressure-sensitive adhesive are lowered and it cannot be actually used. Therefore, it is said that the softening point of the pure monomer resin is preferably about 70 to 100 ° C.

Among the above pure monomer resins, an alkylstyrene-based resin obtained by polymerizing alkylstyrenes such as α-methylstyrene, vinyltoluene, and isopropenyltoluene has good color tone, adhesive property, and molecular weight distribution. It is being awarded for its narrow width and excellent compatibility. However, the alkyl styrenes, which are the raw material monomers, are not preferable because they are not easily available and the cost is high.

On the other hand, styrene monomers are easily available, but styrene polymers have not been widely used as tackifying resins. The reason is that the styrene polymer has a wide molecular weight distribution range and has a relatively high content of high molecular weight substances.
It is presumed that this is because the compatibility with the base polymer is lowered.

As a means for improving the compatibility with the base polymer, for example, a method of reducing the molecular weight of the tackifying resin can be mentioned. However, in such a method, the softening point of the resin is also lowered, so that the obtained tacky adhesive aggregates Insufficient strength and heat resistance.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention aims to overcome the drawbacks of conventional styrene polymers. That is, it is an object of the present invention to provide a method for producing a styrene polymer capable of simultaneously satisfying various properties such as color tone, compatibility with a base polymer, and tackifying effect required as a tackifying resin.

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the problems of the above-mentioned conventional techniques. As a result, when performing a cationic polymerization using a specific amount of a specific monomer component together with styrene and a specific solid acid as a cationic polymerization initiator,
The present invention has been completed by finding that a styrene polymer having a narrow molecular weight distribution width that can simultaneously satisfy various performances required for a tackifying resin can be obtained.

That is, the present invention, in the cationic polymerization of styrene, in the solvent, 0.5 to 10 wt% with respect to the total amount of monomers charged
Α-methylstyrenes and / or α-having 5 or more carbon atoms
The present invention relates to a method for producing a styrene polymer, which comprises polymerizing using activated clay as a polymerization initiator in the presence of an olefin.

In the present invention, α-methylstyrenes and / or α-olefins having 5 or more carbon atoms (hereinafter referred to as modified monomer components) are used as monomer components other than styrene. Examples of α-methylstyrenes include those represented by the general formula [In the formula, R represents a hydrogen atom or a lower alkyl group. ] The compound etc. which are represented by these can be mentioned. The lower alkyl group represented by R in the above general formula (1) is a linear or branched alkyl group having about 1 to 6 carbon atoms such as methyl, ethyl, propyl, butyl, tert-butyl, pentyl and hexyl. A group can be mentioned. Specific examples of the α-methylstyrenes represented by the above general formula (1) include α-methylstyrene and dimethylstyrene. Examples of the α-olefin having 5 or more carbon atoms include diisobutylene, triisobutylene, nonene, decene and polybutene. Among these, α-olefins having about 8 to 15 carbon atoms can be preferably used in consideration of reactivity, availability and the like.

The polymerization behavior in the cationic polymerization of the above-mentioned modified monomer component, the influence on the tackifying property, etc. are not yet known, but of course it is a copolymerization component with styrene and also functions as a chain transfer agent. Presumed to be. It is considered that a styrene polymer having a narrow molecular weight distribution can be obtained by the function of the modifying monomer component.

Although compounds such as vinyltoluene and ethylvinylbenzene are similar to the above α-methylalkylstyrene,
Even if such a compound is used, a styrene polymer having a narrow molecular weight distribution cannot be obtained.

The charging amount of the reforming monomer component is 0.5 to 10 of the total amount of the charging monomer (the total amount of styrene and the reforming monomer component).
The weight may be set to 0.5% by weight, preferably 0.5 to 7% by weight. If it exceeds 10% by weight, the molecular weight of the obtained styrene polymer decreases, and the adhesive strength of the adhesive decreases. On the other hand, when it is less than 0.5% by weight, the width of the molecular weight distribution of the obtained styrene polymer is not narrowed sufficiently, and the compatibility with the base polymer becomes insufficient.

In the present invention, activated clay is used as the cationic polymerization initiator. The desired molecular weight distribution width can be obtained even by using Friedel-Crafts type catalysts such as aluminum chloride and boron trifluoride, which are conventionally used in the production of styrene polymers, and solid acid catalysts such as silica-alumina and ion exchange resins. It is not possible to obtain a styrene polymer having Activated clay is a known catalyst obtained by treating clay with an acid to increase its activity, and can be produced according to a known method. For example, it is produced by drying natural acid clay or clay similar thereto at room temperature to pulverize it, heating the obtained powder with an acid by heating under normal pressure or pressure, and then rinsing, washing with water and drying. it can. Commercially available products of activated clay can be used in the present invention, for example, Galleon Earth NV, Galleon Earth V2, Galleon Earth H, Shilton CS-1, Shilton CS-2 (trade name, all manufactured by Mizusawa Chemical Industry Co., Ltd.) Can be mentioned.

The amount of the activated clay in the present invention is not particularly limited and may be appropriately selected, but is usually about 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the total amount of the charged monomers, and preferably 0.1.
~ 2.0 parts by weight. The method for charging the activated clay is not particularly limited, and either batch or divided charging can be adopted.
If it is less than 0.1 part by weight, the reaction time becomes extremely long, and if it exceeds 5.0 parts by weight, the cost becomes high, which is not preferable.

The cationic polymerization method in the present invention is not particularly limited, and any known method can be adopted. Specific examples thereof include a bulk polymerization method and a solution polymerization method. The solution polymerization method is particularly preferable because it is easier to suppress heat generation as compared with the bulk polymerization method.

Cationic polymerization is carried out, for example, in the presence or absence of an inert gas after charging the reaction vessel with the predetermined amount of styrene, the modifying monomer component, activated clay and a suitable solvent.

As the solvent, it is preferable to use an inert solvent which does not reduce the catalytic activity of the activated clay. Specifically, an inert solvent whose dielectric constant is usually in the range of 1.9 to 2.6 is suitable, and more specifically, benzene, toluene, aromatic solvents such as xylene, alicyclic solvents such as cyclohexane, etc. It can be illustrated.
Among the solvents, when one having a relatively large dielectric constant is used, the obtained styrene polymer tends to have a large molecular weight, and therefore the amount of the modified monomer used is the total amount of all monomers. It is preferable to set it to about several% to 10%.
On the other hand, when a solvent having a low dielectric constant is used, the amount of the modified monomer used is preferably about 0.5 to several percent.

The polymerization temperature is not particularly limited, but usually about 40 to 100 ° C,
The reaction time is preferably about 50 to 80 ° C. and the reaction time is about 1 to 8 hours. When it is lower than 40 ° C, the reaction rate is remarkably lowered and the polymerization yield is also lowered. On the other hand, when the temperature exceeds 100 ° C, it becomes difficult to control the heat of polymerization. After completion of the reaction, the activated clay can be easily removed by over-operation, and when a solvent is used, it can be easily removed under normal pressure or reduced pressure.

Thus, a colorless and transparent styrene polymer having a number average molecular weight of about 600 to 1,000 and an Mw / Mn of 1.7 or less is obtained.
When the number average molecular weight and Mw / Mn are within the above ranges, the softening point of the styrene polymer is usually in the range of 70 to 100 ° C, which means that the styrene polymer has an optimum softening point as a tackifier. When the number average molecular weight is less than 600, the adhesive force and cohesive force are lowered, and when it exceeds 1,000, both tack and compatibility are lowered, which is not preferable. Also, when Mw / Mn exceeds 1.7, tack and compatibility are deteriorated, which is not preferable.

By combining the styrene polymer of the present invention with a base polymer such as an acrylic polymer or a styrene-butadiene-styrene block copolymer, a pressure-sensitive adhesive can be provided, and an ethylene-vinyl acetate copolymer (acetic acid It is also possible to provide a hot melt adhesive by combining a vinyl content of 40% by weight or more) and the like.

The styrene polymer obtained by the method of the present invention can be used not only as a tackifying resin, but also has a narrow molecular weight distribution width. Therefore, when used as a pigment dispersant, the dispersion viscosity is significantly reduced, and the excellent dispersibility is obtained. Can be demonstrated. In addition, when applied as a plastic modifier, it can improve processing suitability at low temperatures and can also be used as a modifying component of epoxy-based and acrylic-based paints, clearly showing the effect of improving the adhesion of coating films. Is recognized.

EFFECTS OF THE INVENTION According to the method of the present invention, it is possible to produce a styrene polymer having a narrow molecular weight distribution range, which has extremely good compatibility with various base polymers as compared with conventional styrene polymers. The styrene polymer is, for example, an acrylic polymer, ethylene-
It has excellent compatibility with various base polymers that are polar polymers such as vinyl acetate copolymers and styrene-butadiene-styrene block copolymers, and is comparable to α-methylstyrene polymers. Moreover, since styrene, which is inexpensive and excellent in raw material availability, is used as a raw material, it is possible to provide an end user with a tackifier which is inexpensive and does not lack supply. Further, the polymer can be suitably used as a pigment dispersant, a plastic modifier, an additive for paints and the like.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to these examples. In the examples, parts and% are based on weight unless otherwise specified.

Example 1 In a reactor equipped with a stirrer, a cooling pipe and a nitrogen introducing pipe,
282 parts styrene, 18 parts α-methylstyrene and 1 toluene
After charging 29 parts, the temperature in the system was raised to about 60 ° C. with stirring under a nitrogen stream. Then, the cationic polymerization reaction was carried out at the same temperature while charging 1.5 parts of activated clay in a divided manner.
Time continued. The temperature was further raised to 80 ° C. over 1 hour, 1.5 parts of activated clay was charged, and the reaction was completed by maintaining the same temperature for 1 hour.

After the reaction was completed, the activated clay was removed and toluene was distilled off under reduced pressure to obtain a colorless transparent polymer. The number average molecular weight of the produced polymer was 700, Mw / Mn was 1.68, the softening point was 80 ° C., the color tone (Hazen color) was 30H, and the yield was 97.5%.

The number average molecular weight and Mw / Mn of the produced polymer are obtained by GPC measurement under the following conditions and polystyrene conversion.

Measuring device: HLC-802A Column: G-4000H8 and G-2000H8 are connected in series. All of the above are manufactured by Toyo Soda Kogyo.

Example 2 A reactor similar to that of Example 1 was charged with 285 parts of styrene, 15 parts of diisobutylene and 129 parts of toluene, then heated to 60 ° C. under a nitrogen stream and charged with 1.5 parts of activated clay in portions. Thereafter, the same operation as in Example 1 was carried out to carry out polymerization to obtain a colorless transparent polymer. The physical properties of the polymer thus obtained are shown in Table 1.

Example 3 A reactor similar to that of Example 1 was charged with 297 parts of styrene, 3 parts of α-methylstyrene and 129 parts of toluene, and then heated to 50 ° C. under a nitrogen stream to divide 1.5 parts of activated clay. After charging, polymerization was carried out in the same manner as in Example 1 below to obtain a colorless transparent polymer. The physical property value of the obtained polymer is the first
Shown in the table.

Example 4 After charging 270 parts of styrene, 30 parts of diisobutylene and 129 parts of toluene into the same reactor as in Example 1, the temperature was raised to 80 ° C. under a nitrogen stream, and 3.0 parts of activated clay was added under the same temperature. Polymerization was carried out while dividing and charging over time to obtain a colorless transparent polymer. The physical properties of the polymer thus obtained are shown in Table 1.

Example 5 Polymerization was performed in the same manner as in Example 1 except that dimethylstyrene was used instead of α-methylstyrene to obtain a colorless transparent polymer. The physical properties of the polymer thus obtained are shown in Table 1.

Example 6 Polymerization was performed in the same manner as in Example 2 except that triisobutylene was used instead of diisobutylene to obtain a colorless transparent polymer. The physical properties of the polymer thus obtained are shown in Table 1.

Comparative Example 1 After charging 270 parts of styrene, 30 parts of diisobutylene and 450 parts of toluene into the same reactor as in Example 1, the temperature was raised to 70 ° C. under a nitrogen stream and boron trifluoride-etherate was added.
The reaction was performed for 3 hours at the same temperature while dropping 9 parts (0.6 part in terms of boron trifluoride). Then, raise the temperature to 80 ℃ and
It was kept warm for a while to complete the reaction. Calcium hydroxide
After deactivating the catalyst by adding 3.5 parts, calcium hydroxide was removed and the solvent was removed to obtain a colorless transparent polymer. The physical properties of the polymer thus obtained are shown in Table 1.

Comparative Example 2 A reactor similar to that of Example 1 was charged with 270 parts of styrene, 30 parts of diisobutylene and 300 parts of toluene, then heated to 60 ° C. under a nitrogen stream and 0.9 parts of aluminum chloride was dividedly charged. The reaction was carried out at the same temperature for 3 hours. afterwards,
The temperature was further raised to 80 ° C., and the temperature was kept for 1 hour to complete the reaction. After 0.6 part of calcium hydroxide was added to deactivate the catalyst, the calcium hydroxide was removed to obtain a pale yellow transparent polymer as a solvent. The physical properties of the polymer thus obtained are shown in Table 1.

Comparative Example 3 Polymerization was carried out in the same manner as in Example 1 except that an ion exchange resin [trade name "Diaion HPK-16", manufactured by Mitsubishi Kasei Co., Ltd.], which was a solid acid catalyst, was used instead of activated clay. After that, a colorless transparent polymer was obtained. The physical properties of the polymer thus obtained are shown in Table 1.

Comparative Example 4 Polymerization was performed in the same manner as in Example 1 except that α-methylstyrene was not used to obtain a colorless transparent polymer. The physical properties of the polymer thus obtained are shown in Table 1.

Comparative Example 5 Polymerization was performed in the same manner as in Example 1 except that the amount of α-methylstyrene charged was 39 parts to obtain a colorless transparent polymer. The physical properties of the polymer thus obtained are shown in Table 1.

Comparative Example 6 Polymerization was performed in the same manner as in Example 1 except that vinyltoluene was used in place of α-methylstyrene to obtain a colorless transparent polymer. The physical properties of the polymer thus obtained are shown in Table 1.

(Performance Test) The performances of the various polymers produced in the above Examples and Comparative Examples were evaluated by the following methods.

Compatibility A blend of base polymer / styrene polymer (weight ratio) = 1/1 was prepared, and a film having a thickness of about 200 μm was prepared using this, and the transparency was visually judged according to the following criteria. However, if the base polymer is acrylic resin, the above ratio should be
8/2

O: Completely transparent B: Slightly opaque X: Opaque The acrylic resin is a copolymer obtained by copolymerizing butyl acrylate / acrylic acid = 97/3 (weight ratio). Ethylene-vinyl acetate copolymer is Mitsui Polychemical Co., Ltd., trade name "EVA # 220" (vinyl acetate content 28%), styrene-butadiene-styrene block copolymer Shell Chemical Co., Ltd., The product name "Clayton 1102" was used.

Adhesive properties A 50 wt% toluene solution of a blend of acrylic resin / styrene polymer (weight ratio) = 9/1 was prepared. The solution is applied to a polyethylene film with an applicator, and the temperature is 105 ° C.
After drying for 5 minutes, a test piece having a thickness of the coating film after drying of 40 μm was obtained.

Compliant with Tack PSTC-6. The measurement temperature was 20 ° C.

According to heat resistance PSTC-7, the time until the test piece slips off was measured. The measurement conditions are a temperature of 40 ° C, a load of 1 kg, and an attachment area of 25 mm.
It was set to 25 mm and a stainless plate was used as the adherend.

Claims (3)

[Claims] 1. When cationically polymerizing styrene, the presence of 0.5 to 10% by weight of α-methylstyrenes and / or α-olefin having 5 or more carbon atoms in the solvent, relative to the total amount of charged monomers. A method for producing a styrene polymer, characterized in that activated clay is used as a polymerization initiator below for polymerization. 2. The production method according to claim 1, wherein the solvent is an inert solvent having a dielectric constant of 1.9 to 2.6. 3. The number average molecular weight of the obtained styrene polymer is
600-1000, weight average molecular weight / number average molecular weight 1.7
The manufacturing method according to claim 1, which is as follows.