JPH03217477A - Production of acrylic tacky agent of solvent type - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing a solvent-based acrylic adhesive.

(Prior Art) Solvent-type acrylic pressure-sensitive adhesives have excellent adhesive properties such as adhesive force and cohesive force, as well as weather resistance and oil resistance, and are widely used, for example, in the production of pressure-sensitive adhesive tapes or sheets.

This type of solvent-based acrylic adhesive is generally (meth)
It is produced by solution polymerizing a vinyl monomer whose main component is an acrylic acid alkyl ester using a peroxide or an azo thermal polymerization initiator.

In such polymerization methods, heat of polymerization is generated, so if temperature control such as heat removal is not performed appropriately, the thermal polymerization initiator will rapidly decompose due to the accumulated polymerization heat and the polymerization reaction will accelerate. This progresses over time, resulting in a decrease in the molecular weight of the polymer and a runaway reaction.

Therefore, the polymerization temperature is generally in a narrow range of about 60 to 70°C, and the polymerization time is generally about 7 to 8 hours, so that the reaction is carried out slowly, which poses the problem of poor productivity.

On the other hand, a liquid material prepared by adding a photopolymerization initiator to a vinyl monomer containing (meth)acrylic acid alkyl ester as a main component is applied or impregnated onto a base material, and the above vinyl heptanomer is irradiated with ultraviolet rays. A method of producing an acrylic pressure-sensitive adhesive tape or sheet through a polymerization reaction is known.

Since this polymerization method performs photopolymerization without using a solvent, only liquid vinyl monomers that are compatible with each other can be used. Therefore, the types of vinyl monomers that can be used are limited, and there is a problem that the ability to respond to the wide variety of needs required for adhesive tapes or sheets is weak.

(Problems to be Solved by the Invention) The present invention solves the above problems, and its purpose is to provide a solvent with excellent adhesive performance such as adhesive force and cohesive force, as well as weather resistance and oil resistance. An object of the present invention is to provide a method for manufacturing a molded acrylic pressure-sensitive adhesive with high productivity.

(Means for Solving the Problems) The method for producing a hot-spring type acrylic pressure-sensitive adhesive of the present invention comprises a monomer consisting of a vinyl monomer containing an alkyl (meth)acrylic acid ester as a main component, a solvent, and a photopolymerization initiator. The method is characterized in that the solution is irradiated with ultraviolet rays to polymerize the vinyl monomer, thereby achieving the above object.

In the present invention, the vinyl monomer containing (meth)acrylic acid alkyl ester as a main component is generally 100 to 60% by weight of (meth)acrylic acid alkyl ester and 0 to 40% by weight of other vinyl monomer copolymerizable therewith. It consists of 4% heavy weight. As the (meth)acrylic acid alkyl ester, a (meth)acrylic acid alkyl ester in which the alkyl group has 1 to 14 carbon atoms, preferably 4 to 12 carbon atoms is used, such as n-butyl (meth)acrylate, ( 2-ethylhexyl meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, and the like are preferably used.

In addition, other vinyl monomers that can be copolymerized with the above (meth)acrylic acid alkyl ester include acrylic acid, methacrylic acid, acrylamide, acrylonitrile, methacrylonitrile, N-monosubstituted acrylamide, and hydroxydiethyl acrylate. , N-vinylpyrrolidone, maleic acid miitaconic acid, N-methylolacrylamide, hydroxyethyl methacrylate, and the like. In addition, a polymer with a low glass transition temperature can be obtained.
Vinyl monomers such as tetrahydrofurfuryl acrylate, polyethylene glycol acrylate, and polypropylene glycol acrylate can also be used.

Solvent-type acrylic pressure-sensitive adhesives are generally often blended with a crosslinking agent during use in order to enhance cohesive strength, heat resistance, solvent resistance, and the like. In this case, as the other vinyl monomer copolymerizable with the (meth)acrylic acid alkyl ester, a vinyl monomer having a carpoxyl group or a hydroxyl group is used.

Solvents used in the present invention include esters such as ethyl acetate, which are commonly used in solution polymerization, ketones such as acetone and methyl ethyl ketone, aromatic hydrocarbons such as toluene, and cyclohexane. The above-mentioned vinyl monomer is dissolved by these solvents. Generally, it is preferable that such a solvent is used in an amount of 50 to 150 parts by weight based on 100 parts by weight of the vinyl heptanomer.

As the photopolymerization initiator, one having an active site within a wavelength range of 300 to 400 nm (nanometers) and having high initiation efficiency is preferably used. Examples include benzoin ethyl ether, penzoin isopyl ether, hydroxyl hexylphenyl ketone, benzyl dimethyl ketal, and the like.

These photopolymerization initiators are
It is preferable to add it in a ratio of 0.001 to 1 part by weight based on the weight part. When the amount added is less than 0.001 parts by weight, the photopolymerization initiator is consumed by light energy in the early stage of the reaction, so the monomer tends to remain, which not only causes the odor of the monomer to remain, but also causes aggregation of the adhesive. Power decreases.

On the other hand, when the amount of the photopolymerization initiator exceeds 1 part by weight, the polymerization reaction rate becomes faster, but the decomposition odor of the photopolymerization initiator becomes more intense, and the performance of the pressure-sensitive adhesive decreases and variations become larger.

Further, in the present invention, it is preferable to add a chain transfer agent to the vinyl monomer solution to which a photopolymerization initiator has been added. Addition of a chain transfer agent suppresses variations in the polymerization reaction, precisely adjusts the molecular weight of the polymer, and adjusts the balance of adhesive performance between adhesive force and cohesive force to a higher level.

As the chain transfer agent, those having high chain transfer properties such as thiol compounds and halogen compounds are preferably used. Examples of thiol compounds include n-dodecyl mercaptobutane, 2-mercaptoethanol, β-mercaptopropionic acid, and β-mercaptoethanol.
-Octyl mercaptopropionate, methoxybutyl β-mercaptopropionate, trimethylolpropane tris(β-thiopropionate), butyl thioglycolate, propanethiols, butanethiols, thiophosphites, and the like. Examples of halogen compounds include carbon tetrachloride.

Such a chain transfer agent is used to transfer the vinyl monomer 1 to -1111Q under conditions that allow a sufficiently high molecular weight polymer to be obtained.
It is preferable to add in a range of 0.2 XIO-' to IOXIO-' moles per mole. This addition amount is 0.2
When X is less than 10-' moles, the molecular weight of the polymer becomes large and the adhesive performance may deteriorate. On the other hand, if the amount of chain transfer agent added exceeds 10 XIO-' moles, the molecular weight of the polymer is too small, and even if the cohesive force is increased by adding a crosslinking agent during use, the adhesive performance will be unbalanced. There is. The weight average molecular weight of the polymer is 30 to 100
It is preferable to adjust it to 1,000,000, and more preferably to adjust it to 600,000 to 1,000,000.

Further, in the present invention, commonly used compounding agents such as a thickener, a thixotropic agent, an extender, and a filler may be added to the vinyl monomer solution to which a photopolymerization initiator has been added.

Thickeners include acrylic rubber and shrimp chlorohydrin rubber, and chickentrope agents include Aerosil and polyvinylpyrrolidone. In addition, fillers include calcium carbonate, titanium, clay, etc., and fillers include inorganic hollow bodies such as glass balloons, alumina balloons, and ceramic balloons, organic spherical bodies such as nylon beads, acrylic beads, silicon beads, and chloride. There are organic hollow bodies such as vinylidene balloons and acrylic balloons, and short fibers such as polyester, rayon, and nylon.

The monomer solution consisting of a vinyl monomer mainly composed of (meth)acrylic acid alkyl ester, a solvent, and a photopolymerization initiator prepared as described above is treated with nitrogen gas or the like in order to remove dissolved oxygen. Purged with inert gas.

Further, without purging with inert gas, a compound having an oxygen removing effect such as phenyl diisodecyl phosphite, triisodecyl phosphite, or octyltin compound may be added.

Then, put the above vinyl monomer solution into the reactor,
This is irradiated with ultraviolet rays to perform a polymerization reaction. The reactor used for the polymerization reaction may be made of quartz glass or Pyrex glass, but one made of Pyrex glass is preferred because it allows ultraviolet irradiation to easily pass through.

The ultraviolet lamp used for irradiation has a wavelength of 300~
Those with a spectral distribution in the 400 nm eI range are used, examples of which include chemical lamps, black light lamps (trade name of Toshiba Electric Materials ■), low-pressure, high-pressure, ultra-high-pressure mercury lamps, metal halide lamps, etc. be.

When irradiating ultraviolet rays with relatively low light intensity, the first two lamps are used, and when irradiating ultraviolet rays with relatively high light intensity, the last four lamps are used.

The light intensity and irradiation time are set depending on the molecular weight and molecular weight distribution, depending on the required quality of the target adhesive. Increasing the light intensity lowers the molecular weight of the polymer, but shortens the polymerization reaction time.

Conversely, when the light intensity is lowered, the molecular weight of the polymer becomes higher, but the polymerization reaction time becomes longer.

In the present invention, ultraviolet rays are irradiated with a wavelength of 300 to 400 nm (nanometers) and a light intensity of 0.1 to 1000 mW (mW)/C111, preferably 0.1 to 100 mW (milliwatts)/C4. . Generally, irradiation time of about 1 to 5 hours is sufficient. The polymerization temperature is generally from room temperature to about 80°C.

When it is necessary to remove heat such as polymerization heat, it is carried out by air cooling or water cooling of the reactor or by adjusting the light intensity.

In particular, in the present invention, a two-step irradiation method is preferred. In this case, the first stage of ultraviolet irradiation has a wavelength of 30
It is carried out at a light intensity of 0.1 to 30 mW/c4 at a wavelength of 0 to 400 nm. This first stage of irradiation polymerizes at least 90% of the vinyl monomer. In this first stage of irradiation, up to about 90% by weight of the vinyl monomer undergoes a relatively rapid polymerization reaction, yielding a high molecular weight polymer. However, the polymerization reaction of the remaining vinyl monomer takes a long time under the above first stage irradiation conditions.

The second stage of irradiation is carried out at a wavelength of 300-400 nm and at a higher light intensity than the first stage of irradiation. The light intensity in this case is preferably at least twice the light intensity in the first stage. In this second stage of irradiation, the remaining vinyl monomer undergoes a rapid polymerization reaction, and the remaining monomer is approximately 3% by weight or less and has almost no adverse effect on adhesive performance.
The polymerization reaction is substantially completed.

In this way, the solvent-based acrylic pressure-sensitive adhesive of the present invention is obtained. This solvent-based acrylic pressure-sensitive adhesive can be used as is or by adjusting the solvent concentration and viscosity. Preferably, this solvent-type acrylic pressure-sensitive adhesive is used with a crosslinking agent added thereto.

As such a crosslinking agent, polyisocyanate, epoxy resin, melamine resin, polyvalent metal salt, etc. are used.

In this case, heating is necessary because a crosslinking reaction occurs due to thermal curing.

This heating also evaporates the solvent in the adhesive.

These crosslinking agents are generally blended in a proportion of 0.001 to 5 parts by weight per 100 parts by weight of the polymer component of the solvent-type acrylic pressure-sensitive adhesive. This increases the adhesive performance, especially the cohesive strength at high temperatures, and improves the cohesive strength at high temperatures.

(Function) In the present invention, when producing a solvent-based acrylic adhesive,
Because it uses a photopolymerization initiator and no thermal polymerization initiator,
There is no rapid decomposition of the polymerization initiator due to polymerization heat, so the polymerization reaction does not run out of control.

In addition, the photopolymerization initiator is decomposed by irradiation with ultraviolet rays, thereby starting the polymerization reaction, so it is possible to adjust the irradiation of ultraviolet rays and quickly polymerize at a relatively low temperature. An adhesive consisting of a sharp polymer is obtained.

Furthermore, since a solvent is used in polymerization by ultraviolet irradiation, by appropriately selecting this solvent,
It becomes possible to dissolve various liquid or solid vinyl monomers containing (meth)acrylic acid alkyl ester as a main component, expanding the selection range of vinyl monomers.

(Example) Examples and comparative examples of the present invention are shown below.

94 parts by weight of 2-ethylhexyl acrylate, 0.5 parts by weight of hydroxyethyl methacrylate, and 5.5 parts by weight of acrylic acid were mixed with 100 parts by weight of ethyl acetate as a solvent and 0.0 parts by weight of benzyl dimethyl chloride as a photopolymerization initiator. Add 1 part by weight and 0.01 part by weight of lauryl mercabutane as a chain transfer agent, and charge this into a five-necked flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel, and a nitrogen gas inlet.
After stirring and dissolving, the monomer solution is purged with nitrogen gas for about 30 minutes to remove oxygen dissolved in the monomer solution.

After that, while replacing the air in the flask with nitrogen gas and stirring, a chemical lamp was used to replace the air in the flask with a light intensity of 4 mW/
All (wavelength: 360 nm) ultraviolet rays were irradiated for about 1.5 hours. Then, using an ultra-high pressure mercury lamp (Jet Cure, manufactured by Oak Seisakusho), the light intensity was 8 mW/ci.
The monomer was polymerized by irradiating ultraviolet light (wavelength: 360 nm) for 0.5 hours to produce a solvent-based acrylic pressure-sensitive adhesive. The total polymerization reaction time was 2 hours.

Regarding the polymer component of the above-mentioned pressure-sensitive adhesive, the weight average molecular weight (S), number average molecular weight (M,), and amount of residual monomer were measured. The molecular weight distribution of the polymer is determined by the degree of dispersion (M, /M.)
The smaller the degree of dispersion, the sharper the molecular weight distribution.

In addition, toluene diisocyanate (TDI) was used as a crosslinking agent in an amount of 0.4 to 100 parts of the polymer component of the above-mentioned adhesive.
After mixing the parts by weight and stirring thoroughly, apply 23% to the release liner.
Coated and dried to a thickness of 38 μm, transferred to a 38 μm polyethylene terephthalate film, and then 40"
An adhesive tape with a width of 25 mm was prepared by heat aging at C for 7 hours. The adhesive performance (adhesive force and holding force) of this adhesive tape was measured.

The above results are shown in Table 1. The measurement method is as follows.

(1) Weight and number average molecular weight Measurement was performed by gel permeation chromatography using standard cross-linked polystyrene as a reference, using tetrahydrofuran as an eluent, and detection using a refractometer.

(2) Residual monomer amount chloro carrying polyethylene glycol (20M)
A gas chromatograph (GC-6
A, manufactured by Shimadzu Corporation).

Note that the measurement sample was adhesive sample 10 in which the solvent had been evaporated.
2 cc from a solution of 0■ dissolved in 5 cc of methyl acetate.
was collected, and 2 cc of this solution was mixed with 2 cc of an internal standard solution prepared by dissolving 2-ethylhexyl methacrylate in methyl acetate to prepare a solution.

(3) Adhesive strength In accordance with JIS Z 0237, a 120 mm long part from one end of an adhesive tape with a width of 25III1 and a length of 300 mm was placed on a steel plate polished with #280 sandpaper using a 2 kg roller. At 23°C and 50% RH, the other end of this tape was peeled off in the opposite direction at a 180 degree angle using an Instron tensile tester at a speed of 300 mm/min (D). Peel resistance (g/25 mm width) was measured.

(4) Holding force In accordance with JIS Z 0237, one end of the adhesive tape with a width of 25mm is attached to a sanded steel plate of #28o using a 2kgO roller so that the adhesion area is 25mm in width and 25mm in length. Fix a weight of 1 kg to the bottom end of the tape, hang it at an ambient temperature of 40°C, measure the time it takes for the adhesive tape to fall, and if it does not fall within 24 hours, , shifted distance (In]n
) was measured.

Northern comparison■↓ 94 parts by weight of 2-ethylhexyl acrylate, 0.5 parts by weight of hydroxyethyl methacrylate, 5.5 parts by weight of acrylic acid, 100 parts by weight of ethyl acetate as a solvent, and 0.01 parts by weight of lauryl mer-butane as a chain transfer agent. Part by weight was added to a five-necked flask equipped with a stirrer, reflux condenser, thermometer, dropping funnel, and nitrogen gas inlet, and purged with nitrogen gas for about 30 minutes to remove oxygen dissolved in the monomer solution. Remove.

After that, the air in the flask was replaced with nitrogen gas, the temperature was raised while stirring, and the temperature was maintained at 60°C, and 15 g of a 0.1% ethyl acetate solution of azoisobutyronitrile was added to the dropping funnel as a thermal polymerization initiator. Drip more gradually. To prevent runaway, 15 g of the same thermal polymerization initiator solution as above was gradually added dropwise from the dropping funnel at intervals of 2 hours.

Furthermore, in order to remove residual monomers after 2 hours, 15 g of a 1% ethyl acetate solution of the same thermal polymerization initiator as above was gradually added dropwise from the dropping funnel, and after the addition was completed, the polymerization reaction was maintained at 60"C for 2 hours. The polymerization reaction time was 7 hours in total.

Hereinafter, in the same manner as in Example 1, the weight average molecular weight (shi) and number average molecular weight group of the polymer component of the adhesive are calculated. ), the amount of residual 1,000 niobium was measured, and the adhesive performance (adhesive strength and holding power) of the adhesive tape was also measured. The results are shown in Table 1.

47 parts by weight of 2-ethylhexyl acrylate, 47 parts by weight of n-butyl acrylate, 6 parts by weight of acrylic acid, 130 parts by weight of acetone as a solvent, and 0.1 part by weight of benzyldimethylkecoel as a photopolymerization initiator. Example 1 was carried out in the same manner as in Example 1, except that a monomer solution containing 0.06 parts by weight of lauryl mercabutane as a chain transfer agent was used.

Regarding the polymer component of the obtained adhesive, the weight average molecular weight (MW), D average molecular weight (M,
), the amount of residual monomer was measured, and the adhesive performance (adhesive force and holding power) of the adhesive tape was also measured. The result is the first
Shown in the table.

Comparison I To 47 parts by weight of 2-ethylhexyl acrylate, 47 parts by weight of n-butyl acrylate, and 6 parts by weight of acrylic acid, 130 parts by weight of acetone as a solvent and 0.06 parts by weight of lauryl mer-butane as a chain transfer agent were added. The monomer solution is then charged into a five-loop flask equipped with a stirrer, reflux condenser, thermometer, addition funnel, and nitrogen gas inlet, and purged with nitrogen gas for about 30 minutes to remove oxygen dissolved in the monomer solution.

After that, the air in the flask was replaced with nitrogen gas, the temperature was raised while stirring, and the temperature was maintained at 60°C, and 0.5 parts by weight of a 6% acetone solution of benzoyl peroxide was added as a thermal polymerization initiator from the dropping funnel. Drip gradually. To prevent runaway, 0.5 parts by weight of the same thermal polymerization initiator solution as above was gradually added dropwise from the dropping funnel at intervals of 3 hours.

Furthermore, 0.5 parts by weight of the same thermal polymerization initiator solution as above was added twice at 2-hour intervals, and after the dropwise addition was completed, the polymerization reaction was completed by holding at 60°C for 2 hours to complete the polymerization reaction. An adhesive was produced. The total polymerization reaction time was 10 hours.

Hereinafter, in the same manner as in Example 1, the weight average molecular weight (shi), number average molecular weight (M,),
The amount of residual heptamer was measured, and the adhesive performance of the adhesive tape (
Adhesive force and holding force) were measured. The results are shown in Table 1.

Table 1 (blank below) (Effects of the Invention) As described above, the present invention provides a monomer solution consisting of a vinyl monomer containing (meth)acrylic acid alkyl ester as a main component, a solvent, and a photopolymerization initiator. Because the above-mentioned vinyl monomer is polymerized by irradiation with A polymer with a sharp molecular weight distribution can be obtained, and thereby a solvent-based acrylic adhesive with excellent adhesive properties such as adhesive force and cohesive force can be produced with high productivity.

Furthermore, since the method of the present invention photopolymerizes a solution in which the vinyl monomer is dissolved in a solvent, it is possible to dissolve various liquid or solid vinyl monomers by selecting an appropriate solvent. An advantage is that a wide variety of solvent-based acrylic pressure-sensitive adhesives can be produced by changing the vinyl monomer depending on the application.

Claims (1)

[Claims] 1. A solvent type characterized in that a monomer solution consisting of a vinyl monomer whose main component is an alkyl (meth)acrylate ester, a solvent, and a photopolymerization initiator is irradiated with ultraviolet rays to polymerize the vinyl monomer. Method for manufacturing acrylic adhesive.