JP3164860B2 - Method for producing acrylic resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an acrylic resin containing almost no volatile components. More specifically, an acrylic resin having a relatively low molecular weight is obtained by solution polymerization, and a solvent contained in a large amount in the polymerization reaction product mixture, and volatile components such as by-products are removed to remove the acrylic resin. How to get. The acrylic resin obtained by the present invention has fluidity at room temperature and is useful in various fields such as pressure-sensitive adhesives.

[0002]

2. Description of the Related Art Conventionally, rubber-based pressure-sensitive adhesives have been widely used, but rubber-based pressure-sensitive adhesives are insufficient in terms of weather resistance. Therefore, in recent years, acrylic pressure-sensitive adhesives having excellent weather resistance have been developed. The acrylic resin used for this purpose is different from the usual one used for molding materials and the like, and is required to have properties capable of maintaining fluidity even in a normal temperature range. Therefore, the acrylic polymer used for the pressure-sensitive adhesive usually has a low glass transition point (Tg) of about -70 ° C to 0 ° C and a low weight average molecular weight of 500,000 or less.

A solution polymerization method is one of the polymerization methods for acrylic monomers. This solution polymerization is generally carried out under the conditions of a temperature of 80 ° C. to 140 ° C. and a viscosity of several tens to tens of thousands of centipoise in terms of heat balance, suppression of generation of by-products, and polymerization stability. Do. The reaction product mixture obtained by the solution polymerization contains a large amount of volatile components such as solvents and by-products.

[0004]

Conventionally, as a method of efficiently removing volatile components from a reaction product mixture after such a solution polymerization, for example, an object to be treated pressurized to a high pressure is injected into a reduced-pressure atmosphere. A method of volatilization and removal by adiabatic expansion is known. However, in this method, when a large amount of volatile components of 15% by weight or more is contained in the object, it is difficult to reduce the content to about 1% by weight or less.
Also, when an object containing a large amount of volatile components is to be removed by such a method, the apparent volume and the apparent viscosity of the object to be treated are considerably increased due to foaming caused by volatilization. Transport and handling of the products becomes difficult.
In addition, if the conditions of higher temperature and vacuum are used for the purpose of sufficient volatilization and removal, a side reaction or decomposition occurs in the object to be treated, and various by-products may be generated.

On the other hand, as a conventional method for producing an acrylic resin in consideration of the removal of volatile components, for example, JP-A-52-1755.
No. 5 has been proposed. This production process is widely and widely employed because of its high removal efficiency of unreacted monomers and by-products.

However, this conventional method is a method for producing an ordinary acrylic resin used for molding materials which are solid at ordinary temperature, and is a method for producing an acrylic resin having fluidity at ordinary temperature as described above. When used in the above, the resin cannot be collected because the liquid cannot be sent in the extruder. Further, in this conventional method, the resin is heated to a high temperature of 240 ° C. or more, so that when an acrylic resin having fluidity at normal temperature is to be obtained, the resin may be discolored.

[0007] Further, in the case of cooling the acrylic resin having fluidity at normal temperature in the manufacturing process, since the strand cannot be drawn out, water cooled, pelletized, etc., the resin is sandwiched between Teflon-coated belts. Conventionally, there has been known a method of cooling from the outer surface with water or extruding a resin on a belt in a cylindrical shape having a diameter of several centimeters at intervals and cooling from the lower surface of the belt. However, these conventional methods not only increase the size of the apparatus but also reduce the cooling efficiency, and furthermore, it is difficult to take out the resin from the cooling apparatus because the resin exhibits fluidity. Have difficulty.

The present invention has been made to solve the above-mentioned problems. That is, an object of the present invention is a method for producing an acrylic resin by almost removing volatile components from a composition containing an acrylic polymer and also containing a large amount of volatile components, the removal of which is efficient and An object of the present invention is to provide a method which can be performed sufficiently, can easily handle an object to be processed, and can be easily performed with small-scale equipment. Another object of the present invention is to efficiently and sufficiently cool the acrylic resin thus obtained, to easily handle the object to be processed, and to easily perform the process with a small-scale facility. The purpose is to provide a way to gain.

[0009]

SUMMARY OF THE INVENTION The above object of the present invention is as follows.
The volatile component is removed from the acrylic polymer composition containing 5 to 85% by weight of the volatile component to obtain a fluidity at room temperature.
In a method for producing an acrylic resin, the polymer composition is subjected to a pressure of 1 kg / cm ² or more and a temperature of 60 ° C. to 2 ° C.
At a temperature of 20 ° C, internal pressure of 4
The volatile components are volatilized and removed by directly spraying into the supply section of the twin-screw kneader kept at 00 Torr or less, and the barrel temperature of the twin-screw kneader is set to 160 ° C. to 220 ° C. and the internal pressure of the barrel is set to 400 Torr or less. Further, the present invention can be attained by providing a method for producing an acrylic resin, which comprises kneading the polymer composition in a state where the barrel is not filled with the polymer composition to remove residual volatile components.

Another object of the present invention is to provide a resin film having a heat resistance of 110 ° C. or higher by removing the remaining volatile components by kneading with a biaxial kneader as described above. Filled and sealed,
The sealed bag is poured into a cooling liquid of 40 ° C. or less and moved, and / or the sealed bag is moved in an atmosphere under a spray of a cooling liquid of 40 ° C. or less, thereby continuously. This can be achieved by providing a method for producing an acrylic resin having a cooling step.

[0011]

In the present invention, the method for removing volatile components is as follows.
Basically, the object is to volatilize and separate by heating and reducing the pressure of the object. And in the present invention, using a twin-screw kneader, in both the step of spraying the composition in the supply section and the step of kneading in a state where the barrel is not filled, volatilization is separated under predetermined conditions. Do. The combination of the two-stage volatilization and the conditions at that time have a synergistic effect, so that even if a large amount of volatile components is contained, an acrylic resin from which the volatile components have been sufficiently removed can be obtained favorably. Becomes

Furthermore, if the acrylic resin after the volatilization removal is filled into a heat-resistant bag and continuously cooled under specific conditions, the acrylic resin can be obtained efficiently and easily with cooling efficiency. Become.

Hereinafter, the production method of the present invention will be described in more detail.

The method of the present invention has an advantageous effect when used for a composition containing an acrylic polymer and a large amount (15 to 85% by weight) of a volatile component. That is, with respect to a composition having a lower content of the volatile component, sufficient volatilization and removal may be performed by a method other than the present invention in some cases. For example, for a composition containing only 10% by weight or less of a volatile component, the content of the volatile component can be sufficiently removed by using a so-called vent extruder or vent kneader. For example, for a composition containing only 5% by weight or less of a volatile component, it is possible to remove the remaining volatile component to 0.5% by weight or less using a suitably designed vent extruder or kneader. is there. However, 15
For compositions containing large amounts of volatile components of up to 85% by weight, good results are not obtained without according to the invention. Hereinafter, a composition containing such an acrylic polymer and 15 to 85% by weight of a volatile component is referred to as an “acrylic polymer composition”.

The acrylic polymer means various (co) polymers obtained by polymerizing a monomer having an acrylic group or a methacrylic group in a molecule as a main component. Examples of the monomer having an acryl group or a methacryl group in a molecule used for constituting the acrylic polymer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate,
Alkoxy (meth) acrylates such as cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate; 2-hydroxyethyl (meth)
Acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate,
Examples thereof include (meth) acrylic esters having a hydroxyl group such as 4-hydroxybutyl (meth) acrylate. Also, acrylic acid, methacrylic acid, styrene,
Acrylonitrile and the like can also be used in combination.

The acrylic polymer composition is generally obtained as a reaction product mixture after solution polymerization of the acrylic monomer.

Solvents used for producing the acrylic polymer composition by solution polymerization include, for example, toluene, xylene, benzene, hexane, butyl acetate, ethyl acetate having a boiling point in the range of 60 ° C. to 200 ° C. Isopropyl alcohol, butanol, methyl ethyl ketone and the like. The amount of these solvents used is in the range of 85% by weight or less based on the monomer. This polymerization can be carried out at a polymerization temperature of 60 ° C to 160 ° C using a known polymerization initiator, for example, an organic peroxide or an azo catalyst.

The volatile component referred to in the present invention includes low-molecular-weight polymers such as dimers and trimers of monomers formed during polymerization, by-products, solvents used in solution polymerization, and completion of polymerization. Unreacted monomers remaining when not performed.

The method of the present invention is particularly useful when the Tg of the acrylic polymer is in the range of -70 ° C to 0 ° C and the weight average molecular weight is in the range of 20,000 to 500,000. Useful.

In the present invention, the acrylic polymer composition is heated and pressurized to pass through pores or narrow gaps.
It is sprayed on the supply section of the shaft kneader. This spraying can remove most of the volatile components contained in the acrylic polymer composition. This volatile component may be separated from the transport route of the composition and recovered.

The pores or narrow gaps used in the spraying have the effect of causing a necessary pressure loss as a boundary between the high pressure side and the low pressure side, and reduce the flow rate when the composition is discharged to the low pressure side. It also plays a role in raising. The pores or the narrow gaps are not particularly limited, as long as they have a size capable of exerting the above-described effects well.

The pressure during the spraying, that is, the pressure on the high pressure side before passing through the pores or narrow gaps, is 1 kg / cm
² or more. This pressure is preferably higher from the viewpoint of the effect of the present invention. However, the pressure is preferably 4 kg / cm ² or less from the viewpoint of equipment conforming to regulations such as high-pressure gas control and equipment cost.

The temperature of the acrylic polymer composition at the time of this spraying is in the range of 60 ° C. to 220 ° C., preferably 100 ° C. or more. If the temperature is too low, the volatilization of volatile components will be insufficient, and if it exceeds 220 ° C., the resulting acrylic resin will be discolored. As the heating means, a generally used multi-tube heat exchanger or the like can be used, and it is desirable that the heating means is designed to have a small liquid retaining portion. Further, depending on the amount of treatment, a heating jacket can be provided in a pipe section from the polymerization tank to the devolatilizer.

The pressure in the supply section of the twin-screw kneader at the time of the spraying, that is, the pressure on the low pressure side after passing through the fine holes or narrow gaps is set to 400 Torr or less, preferably 100 Torr or less.
It is preferable to perform the process while maintaining the vacuum at Torr or lower.

The acrylic polymer composition blown out from the pores or narrow gaps has an apparent volume increase and bulkiness due to foaming caused by volatilization. The bulked composition is usually difficult to handle in a subsequent step. However, in the present invention, when the composition becomes bulky in the supply section of the twin-screw kneader, the composition is in a state where the composition is directly beaten to the screw in the supply section. Into the barrel.
Therefore, in the present invention, there is no difficulty in handling the bulked composition. In addition, the fact that the temperature of the composition decreases and the viscosity increases due to the influence of the heat of vaporization of the volatile components also has a favorable effect on the entrainment by the screw. If a general single-screw extruder is used instead of a twin-screw kneader, the bulky resin cannot be satisfactorily rolled in as in the present invention.

In the present invention, the positions where the pores or narrow gaps for supplying the acrylic polymer composition are provided are as follows.
It is preferable to set it on the perpendicular bisector of the line connecting the centers of the shaft screws. The screw facing the pore or the narrow gap is preferably a trapezoidal deep groove shaped screw or a corrugated screw having a strong feeding force.

The space between the screw and the pores or narrow gaps may be left as it is, or the same effect can be obtained by providing a pipe between them and forcibly guiding the composition to the screw. . When installing pipes like this,
When the exhaust hole for devolatilization is provided above the position of the end face of the pipe facing the screw, it is effective to prevent the composition from being entrained in the devolatilization line. If you do not install the pipe,
The pores or narrow gaps and the vent holes for devolatilization are preferably separated by at least 30 mm, but the positional relationship is not particularly limited.

In the present invention, the polymer composition sprayed on the supply section as described above is kneaded as it is under a predetermined condition by a twin-screw kneader. By this kneading (that is, stirring in the barrel), the object to be processed is heated and the surface is renewed.
The remaining volatile components can be volatilized and separated.

The shape of the screw at the part where the kneading is performed is such that a convex lens type or a pseudo triangular kneading disk having a strong kneading force can be used even if a trapezoidal deep groove type or a corrugated screw which is the same as the supply unit having a strong feeding force is used. Even if used, the effect of devolatilization can be obtained.

Even when a kneading disk is used, a trapezoidal deep groove type or corrugated screw portion for discharging the devolatilized composition is provided at a position close to the nozzle at the tip of the twin-screw kneader at several pitches. By arranging it separately, it is easy to take out the composition after devolatilization, but when using a helical disk with a processed kneading disk tip, the kneading disk can also generate a feeding force, so this limit Absent.

As the twin-screw kneader, one having an effective screw length / screw diameter (L / D) of 15 or less is preferably used. When a material having a small L / D is used, the residence time of the object to be treated in the barrel is short, and the adverse effect of heat is small. Furthermore, it has the advantages that the equipment is compact, the driving horsepower is small, and the equipment is inexpensive compared to an extruder of the same diameter. The barrel temperature during this kneading is 160 ° C to 220 ° C.
Within the range. If the temperature is lower than 160 ° C., the removal of volatile components becomes insufficient, and if the temperature is higher than 220 ° C., the obtained resin tends to be discolored. 200 ° C to prevent resin coloring
The following is preferred. The pressure in the barrel at the time of the kneading is set to 400 Torr or less, and preferably a vacuum of 100 Torr or less. If this pressure exceeds 400 Torr, the removal of volatile components may be insufficient.

At the time of kneading, it is necessary to supply and knead so that the barrel is not filled with the polymer composition containing the residual volatile components which has been treated by direct spraying in the supply section under the above conditions. . In such a state, the thin film is formed into a thin film by the screw in the barrel, and the separated volatile component moves toward the inside of the supply unit held under reduced pressure, and is taken out to the outside to be well collected. If the inside of the barrel is filled, it becomes difficult to take out and recover volatile components from the barrel.

An acrylic resin containing almost no volatile components through the injection and kneading steps as described above,
Specifically, an acrylic resin having a residual volatile component content of 1% by weight or less can be obtained.

Further, in the present invention, the acrylic resin from which the remaining volatile components have been removed by kneading with a twin-screw kneader is filled into a bag made of a resin film having a heat resistance of 110 ° C. or higher and sealed. Continuously transferring the sealed bag into a cooling liquid at a temperature of 40 ° C. or lower and / or moving the sealed bag in an atmosphere under a spray of a cooling liquid at a temperature of 40 ° C. or lower. It is preferable to perform a cooling step. According to this cooling step, the cooling efficiency is high, and handling in the step is easy.

From the viewpoint of heat capacity, especially when the resin is moved in an atmosphere under the spray of the cooling liquid, the filling amount of the resin in the bag is 1 kg.
The following is desirable. The movement of the cooling liquid in the sprayed atmosphere is performed by, for example, moving the bag while spraying a mist-like or curtain-like cooling liquid onto the bag.

As the bag-like material that can be used in this cooling step, for example, a film made of polypropylene, nylon, polycarbonate, polyester, polyphenylene sulfide, polyetherimide, a fluororesin, or the like, or a laminate thereof can be used. .

[0037]

Embodiments of the present invention will be described below with reference to the drawings. Here, FIG. 1 is a schematic flow sheet of the production process of the acrylic resin employed in the examples.

Example 1 First, raw materials were charged into a polymerization vessel 1 having the following composition.

N-butyl acrylate 52% by weight 2-ethylhexyl acrylate 40% by weight 2-hydroxyethyl methacrylate 3% by weight Acrylic acid 5% by weight Toluene 10%
0 parts by weight After charging, the inside of the polymerization vessel 1 was kept at 110 ° C., nitrogen was injected so that the pressure became equal to the atmospheric pressure, and the polymerization reaction was allowed to proceed for 10 hours. The acrylic polymer composition obtained by this reaction has a volatile component of toluene and by-products of 50%.
The composition occupied% by weight. The weight average molecular weight of the acrylic polymer in this composition was 25,000, and the viscosity of the acrylic resin was 6500 centipoise at 25 ° C.

Subsequently, this acrylic polymer composition was
Pumped into heat exchanger 3 by pump 2 of type WP1AL013 made by Daido Metal Co., and pressure 3 with steam of 5 kg / cm ²
kg / cm ² , after raising the temperature to 110 ° C to 120 ° C,
S2KRC manufactured by Kurimoto Seisakusho through a hole 4 with a diameter of 2 mm
It was sprayed into the supply unit 6 of a twin-screw kneader 5 (L / D = 13.2). A condenser 7 and a vacuum pump 9 were sequentially connected to the supply unit 6, and the inside of the supply unit 6 was maintained at 50 Torr by the vacuum pump 9. By this spraying step, most of the volatile components such as toluene contained in the acrylic polymer composition are volatilized in the supply section 6, and the volatiles are led into the condenser 7 and connected to the condenser 7. The recovered solvent was recovered in the recovered solvent storage tank 8.

The composition sprayed into the supply section 6 was directly introduced into the barrel of a twin-screw kneader and kneaded.
FIG. 2 is a cross-sectional view schematically showing the internal structure of the barrel of the twin-screw kneader used in this embodiment. The supply section 6 is directly connected to the position shown in FIG. 2 inside the barrel, and the composition sprayed into the supply section 6 is fed from this position by the corrugated screw type feed screw 20 in the jacket section 22 to the kneading disk 21. And the surface is agitated and renewed. The feed screw 20 and the kneading disk 21 are driven by a stirring motor 18 connected to a stirring shaft 19.

Here, the barrel temperature was kept at 190 ° C., and the pressure in the barrel was kept at a vacuum of 50 Torr by a vacuum pump 9 connected to the condenser 7 to carry out kneading. As a result, the surface of the composition inside the barrel was renewed, and the remaining toluene and the like volatilized. This volatile matter was also guided from the inside of the barrel into the condenser 7 and collected in the collection solvent storage tank 8. Here, the filling rate of the composition may be 95% or less so that the volatile gas flows well in the stirring section in the barrel. The acrylic resin from which volatile components had been removed in this manner was discharged at about 140 ° C. from the nozzle 11 at the tip of the twin-screw kneader. The residual volatile component of the acrylic resin obtained here was 0.5% by weight.

The acrylic resin discharged from the nozzle portion 11 is continuously supplied to Daido Metal WP1AL01 for resin.
It was filled into a cooling bag 13 via a type 3 pump 12.
As the cooling bag 13, a 100 μm thick film (having a heat resistance of about 150 ° C.) of nylon 6 manufactured by Toyobo Co., Ltd. made by using a heat sealing machine was used. The point of time when the set weight was filled was detected by a weight measuring device installed at the lower part of the cooling bag 13, and at that time, the opening of the cooling bag 13 was sealed with the heat sealing machine 15. In this step, the position of the nozzle portion 11, the position of the pump 12, and the position of filling the cooling bag 13 may be close to each other from the viewpoint of heat dissipation measures. The sealed cooling bag 13 was successively dropped into a water tank 17 (water temperature = approximately 5 ° C. to 40 ° C.) located therebelow, and was cooled by being conveyed by a conveyor 16 installed at a lower portion of the water tank 17. According to this example, it was confirmed that an acrylic resin containing almost no volatile components could be easily produced with a relatively small-scale facility with good handleability.

[0044]

As described above, according to the present invention, the two-stage volatilization of the composition in the supply section of the twin-screw kneader and the kneading in the barrel are performed under specific conditions. In this way, it is easy to handle the processed material, it can be easily performed with small-scale equipment, and even if it contains a large amount of volatile components, it can be efficiently and sufficiently (1% by weight or less)
Acrylic resin can be obtained.

Further, as described above, if the resin is filled in a heat-resistant bag and continuously cooled under specific conditions, the acrylic resin can be easily handled, and simple continuous cooling can be performed with a small-scale facility. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic flow chart of steps adopted in Examples.

FIG. 2 is a cross-sectional view schematically showing a structure in a barrel of the twin-screw kneader used in the embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 polymerization pot 2 pump 3 heat exchanger 4 pore 5 double-screw kneader 6 double-screw kneader supply unit 7 condenser 8 recovery solvent storage tank 9 vacuum pump 11 kneader tip nozzle 12 resin pump 13 cooling bag 14 Weight measuring device 15 Heat sealing machine 16 Conveyor 17 Water tank 18 Stirring motor 19 Stirring shaft 20 Feed screw 21 Kneading disk 22 Jacket part

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-6505 (JP, A) JP-A-5-17516 (JP, A) JP-A-4-313301 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C08F 6/10

Claims (3)

(57) [Claims] 1. A room temperature by removing the volatile components from the acrylic polymer composition comprising 15 to 85 wt% of the volatile components
In the method for producing an acrylic resin having fluidity in the above, the polymer composition is subjected to a pressure of 1 kg / cm ² or more and 6
The volatile components are volatilized and removed by directly spraying through a fine hole or a narrow gap at a temperature of 0 ° C. to 220 ° C. into a supply part of a twin-screw kneader whose internal pressure is maintained at 400 Torr or less. An acrylic resin having a barrel temperature of 160 ° C. to 220 ° C., a barrel internal pressure of 400 Torr or less, and kneading in a state where the polymer composition is not filled in the barrel to remove residual volatile components. Manufacturing method. 2. An acrylic resin from which residual volatile components have been removed by kneading with a twin-screw kneader is filled into a bag made of a resin film having heat resistance of 110 ° C. or higher, and sealed. Into a cooling liquid of 40 ° C. or lower and / or move the sealed bag to 40 ° C.
The method for producing an acrylic resin according to claim 1, further comprising a step of continuously cooling by moving in a sprayed atmosphere of a cooling liquid at a temperature of not more than ℃. 3. The Tg of the acrylic polymer is from -70 ° C. to 0 ° C.
° C and has a weight average molecular weight of 20,000.
3. The method according to claim 1 or 2, wherein the value is in the range of ~ 500,000.
Method for producing acrylic resin .