JPH05148311A - Production of acrylic resin - Google Patents

Abstract

PURPOSE:To easily and sufficiently remove a volatile component, such as a solvent, from an acrylic resin even when it has a high volatile content to thereby attain a residual volatile content of 1wt.% or lower. CONSTITUTION:An acrylic polymer composition having a volatile content of 15-85wt.% is sprayed through an orifice 4 onto a feed part 6 of a twin-screw kneader 5 at 60-220 deg.C under a pressure of 1kg/cm<2>, and is kneaded as it is. Thus, an acrylic resin having a volatile content of almost zero is obtained. The pressure inside the feed part 6 is 400Torr or lower, the barrel temp. is 160-220 deg.C, and the pressure inside the barrel is 400Torr or lower.

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 component. More specifically, a relatively low molecular weight acrylic polymer is obtained by solution polymerization, and the acrylic resin is removed by removing volatile components such as solvents and by-products contained in a large amount in the polymerization reaction product mixture. Regarding how to get. The acrylic resin obtained by the present invention has fluidity at room temperature and is useful in various fields such as adhesives.

[0002]

2. Description of the Related Art Rubber-based adhesives have been widely used as adhesives, but rubber-based adhesives are insufficient in terms of weather resistance. Therefore, in recent years, acrylic adhesives having excellent weather resistance have been developed. The acrylic resin used for this purpose is required to have the property of maintaining fluidity even in the room temperature range, unlike ordinary ones used for molding materials and the like. 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 polymerization conditions of a temperature of 80 ° C. to 140 ° C. and a liquid viscosity of several tens to several tens of thousands centipoise from the viewpoints of heat balance, suppression of by-product generation, polymerization stability and the like. To do. The reaction product mixture obtained by solution polymerization contains a large amount of volatile components such as solvents and by-products.

[0004]

Conventionally, as a method for efficiently removing volatile components from the reaction product mixture after such solution polymerization, for example, a high pressure-pressed object is injected into a reduced pressure atmosphere. A method of removing volatilization by adiabatic expansion is known. However, according to this method, when the object to be treated contains a large amount of volatile components of 15% by weight or more, it is difficult to reduce the content to about 1% by weight or less.
Further, when an object to be processed 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 processed are considerably increased due to foaming caused by the volatilization. Will be difficult to transport and handle.
Further, if the conditions of higher temperature and vacuum are used for the purpose of sufficient volatilization removal, a side reaction or decomposition may occur 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 removing volatile components, for example, Japanese Patent Laid-Open No. 52-1755.
No. 5 is proposed. This manufacturing process is a widely adopted method because of its high efficiency of removing unreacted monomers and by-products.

However, this conventional method is a method for producing a usual acrylic resin which is solid at room temperature and is used for molding materials, and the like, which is a method for producing an acrylic resin having fluidity at room temperature as described above. When used for, the liquid cannot be fed in the extruder and the resin cannot be recovered. Further, in this conventional method, the resin is heated to a high temperature of 240 ° C. or higher, so that when an acrylic resin having fluidity at room temperature is to be obtained, the resin may be discolored.

Further, in the manufacturing process, when the acrylic resin having fluidity at such a room temperature is cooled, strand drawing, water cooling, pelletizing, etc. cannot be performed. Conventionally known are methods of cooling with water from the outer surface, or extruding resin on a belt in a cylindrical shape having a diameter of several centimeters at intervals so that the resin is cooled from the lower surface of the belt. However, in these conventional methods, not only the apparatus becomes large-scale, but also the cooling efficiency is not good, and furthermore, since the resin exhibits fluidity, it is difficult to take out from the cooling apparatus, and the resin after taking out is also handled. Have difficulty.

The present invention has been made to solve the above problems. That is, an object of the present invention is a method for producing an acrylic resin by removing most volatile components from a composition containing an acrylic polymer and also containing a large amount of volatile components, and the removal is efficient and An object of the present invention is to provide a method that can be sufficiently performed, that the object to be treated is easy to handle, and that can be easily performed with a small-scale facility. Another object of the present invention is to cool the acrylic resin thus obtained efficiently and sufficiently, to easily handle the object to be treated, and to carry out it easily with a small-scale facility. It is to provide a method of obtaining.

[0009]

The above objects of the present invention are as follows.
In a method for producing an acrylic resin by removing the volatile component from an acrylic polymer composition containing 5 to 85% by weight of the volatile component, 1 kg / cm ² of the polymer composition is used.
At the above pressure and a temperature of 60 ° C. to 220 ° C., the volatile components are volatilized and removed by directly spraying into the feed section of a twin-screw kneader having an internal pressure of 400 Torr or less through pores or narrow gaps. The barrel temperature of the twin-screw kneader is 160
C. to 220.degree. C., a pressure in the barrel of 400 Torr or less, and kneading in a state in which the polymer composition does not fill the barrel to remove residual volatile components, and to provide a method for producing an acrylic resin. Can be achieved by

Another object of the present invention is to obtain an acrylic resin from which residual volatile components have been removed by kneading with a biaxial kneader as described above, and a resin film having a heat resistance of 110 ° C. or higher. Filled with a bag and sealed,
By continuously moving the sealed bag into a cooling liquid of 40 ° C. or lower, and / or moving the sealed bag in an atmosphere under the spraying of the cooling liquid of 40 ° C. or lower, continuously. This can be achieved by providing a method for producing an acrylic resin having a step of cooling.

[0011]

In the present invention, the method for removing volatile components is
Basically, it is a point to volatilize and separate by heating and decompressing the object to be treated. In the present invention, a twin-screw kneader is used, and volatilization separation is performed under predetermined conditions in both the step of spraying the composition at the supply part and the step of kneading in a state where the barrel is not filled. To do. The combination of these two stages of volatilization separation and the conditions at that time have a synergistic effect on each other, and even if a large amount of volatile components are contained, it is possible to satisfactorily obtain an acrylic resin from which they have been sufficiently removed. Becomes

Furthermore, if the acrylic resin after the volatilization and removal is filled in a bag having heat resistance and continuously cooled under specific conditions, the acrylic resin can be easily obtained with good cooling efficiency. Become.

The manufacturing method of the present invention will be described in more detail below.

The method of the present invention has a significant 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 volatile component content lower than this, there are cases where sufficient volatilization removal can be carried out by a method other than the present invention. For example, for a composition containing only 10% by weight or less of a volatile component, it is possible to sufficiently remove the contained volatile component by using a so-called vent extruder or vent kneader. Further, for example, for a composition containing only 5 wt% or less of volatile components, it is possible to remove residual volatile components to 0.5 wt% or less by a properly designed vent extruder or kneader. is there. But 15
For compositions containing large amounts of volatile constituents of ˜85% by weight, good results cannot be obtained without 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 the molecule as a main component. Examples of the monomer having an acrylic group or a methacrylic group in the molecule used to form the acrylic polymer include 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, stearyl (meth) acrylate, 2-hydroxyethyl (meth)
Acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate,
Examples thereof include (meth) acrylic acid ester having a hydroxyl group such as 4-hydroxybutyl (meth) acrylate. In addition, 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.

The solvent used when the acrylic polymer composition is produced by solution polymerization is, for example, toluene, xylene, benzene, hexane, butyl acetate or ethyl acetate having a boiling point 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 monomers. This polymerization can be carried out at a polymerization temperature of 60 ° C to 160 ° C using a known polymerization initiator such as an organic peroxide or an azo catalyst.

The volatile component as referred to in the present invention is a low molecular weight polymer such as a dimer or trimer of a monomer produced during polymerization, a by-product, a solvent used in solution polymerization and the completion of the polymerization. Unreacted monomers that remain when not used.

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

In the present invention, this acrylic polymer composition is heated and pressed to pass through pores or narrow gaps.
Spray on the supply part of the shaft kneader. By this spraying, most of the volatile components contained in the acrylic polymer composition can be removed. This volatilized component may be recovered by separating it from the transportation route of the composition.

The pores or narrow gaps used during the spraying have the function of causing a pressure loss necessary as a boundary between the high pressure side and the low pressure side, and the flow rate at which the composition is discharged to the low pressure side. It also plays a role to raise. The pores or the narrow gaps are not particularly limited as long as they have a size capable of exhibiting the above-described action well.

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

The temperature of the acrylic polymer composition during this spraying is in the range of 60 ° C to 220 ° C, preferably 100 ° C or higher. If this temperature is too low, the volatilization of the volatile components will be insufficient, and if it exceeds 220 ° C., the resulting acrylic resin will be discolored. As the heating means, a commonly used multi-tube heat exchanger or the like can be used, and it is desirable that the design is such that the liquid retention portion is small. Further, depending on the amount of treatment, it is possible to install a heating jacket in the pipe section from the polymerization tank to the devolatilization device.

The pressure in the supply section of the twin-screw kneader at the time of this spraying, that is, the pressure on the low pressure side after passing through the pores or the narrow gap is 400 Torr or less, preferably 100.
It is advisable to carry out the process while maintaining a vacuum of Torr or less.

The acrylic polymer composition blown out from the pores or the narrow gaps has an apparent volume increased and becomes bulky due to foaming caused by volatilization. The bulky composition is usually difficult to handle in a subsequent step. However, in the present invention, when the composition becomes bulky in the feeding section of the twin-screw kneader, the screw in the feeding section immediately comes into contact with the composition because the composition directly hits the screw in the feeding section. Is introduced into the barrel.
Therefore, the present invention does not cause any difficulty in handling the bulky composition. Furthermore, the fact that the temperature of the composition decreases and the viscosity increases due to the effect of the heat of vaporization of the volatile components also works well for the inclusion by the screw. If a general single-screw extruder is used instead of a twin-screw kneader, the bulky resin cannot be satisfactorily wound as in the present invention.

In the present invention, the positions where the pores or the narrow gaps for supplying the acrylic polymer composition are installed are 2
It is preferable to install on the vertical bisector of the line connecting the centers of the screw of the shaft. The screw facing the pores or the narrow gap is preferably a trapezoidal deep groove-shaped screw having a strong feeding force or a corrugated screw.

The space between the pores or the narrow gap and the screw may be left as it is, or a pipe may be provided between them to forcibly introduce the composition to the screw, and the same effect can be obtained. .. When the pipe is installed like this,
When the exhaust hole for devolatilization is installed above the position of the end face of the pipe facing the screw, it is effective in preventing the composition from being entrained in the devolatilization line. If you do not install the pipe,
It is preferable that the pores or the narrow gap and the exhaust hole for devolatilization are installed at a distance of 30 mm or more, but the positional relationship is not particularly limited.

In the present invention, the polymer composition sprayed onto the supply section as described above is kneaded as it is under a predetermined condition with a biaxial kneader. By this kneading (that is, stirring in the barrel), the object to be treated is heated and the surface is renewed,
Residual volatile components can be volatilized and separated.

Even if the same trapezoidal deep groove type or corrugated type screw as that of the feeding section having a strong feeding force is used, the screw shape of the kneading portion is not limited to the convex lens type or the pseudo triangle type kneading disc having a strong kneading force. 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 part for discharging the devolatilized composition is provided at a few pitches in the portion near the nozzle at the tip of the twin-screw kneader. By providing it, it becomes easy to take out the composition that has been devolatilized, but when using a disc with a helical processed tip portion of the kneading disc, the kneading disc can also generate a feeding force, so this is not the 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 processed 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 it is cheaper than an extruder of the same diameter. The barrel temperature during this kneading is 160 ° C to 220 ° C.
Within the range of. If this temperature is less than 160 ° C, the removal of volatile components becomes insufficient, and if it exceeds 220 ° C, the resulting resin is likely to discolor. 200 ℃ from the viewpoint of preventing resin coloration
The following are preferred. The pressure in the barrel during this kneading is 400 Torr or less, preferably 100 Torr or less. If this pressure exceeds 400 Torr, the removal of volatile components may be insufficient.

During kneading, it is necessary to supply and knead so that the polymer composition containing the residual volatile component treated by direct spraying in the feeding section under the above conditions does not fill the barrel. .. By making such a state, the screw in the barrel thins it, and the separated volatile component moves in the direction of the inside of the supply section held under reduced pressure, and can be taken out from there and satisfactorily recovered. If this barrel is filled up, it will be difficult to take out and collect volatile components from the barrel.

An acrylic resin containing almost no volatile components by the above-mentioned injection and kneading steps,
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 in a bag made of a resin film having a heat resistance of 110 ° C. or higher and sealed. , By continuously moving the sealed bag into a cooling liquid of 40 ° C. or lower, and / or moving the sealed bag in an atmosphere of the cooling liquid of 40 ° C. or lower under spraying. It is preferable to carry out the step of cooling. According to this cooling process, the cooling efficiency is high and the handling in the process is easy.

From the viewpoint of heat capacity, the amount of resin filled in the bag is 1 kg, especially when the cooling liquid is moved in an atmosphere under spraying.
The following is desirable. The movement of the cooling liquid in the sprayed atmosphere is performed, for example, by moving the bag while spraying the mist-shaped or curtain-shaped 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, fluororesin or the like, and 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 manufacturing process of the acrylic resin used in the examples.

Example 1 First, the raw materials were put into the polymerization kettle 1 with 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 to 100 parts by weight of the above total
0 parts by weight After charging this, the inside of the polymerization kettle 1 was maintained 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 contains 50 or more volatile components of toluene and by-products.
The composition accounted for wt%. 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, the acrylic polymer composition was
It is sent to the heat exchanger 3 by the pump 2 of Daido Metal WP1AL013 type and the pressure is 3 by the steam of 5 kg / cm ^2.
kg / cm ² , after raising the temperature to 110 ° C to 120 ° C,
Through the pores 4 with a diameter of 2 mm, S2KRC manufactured by Kurimoto
It was sprayed into the supply section 6 of the mold biaxial 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 component such as toluene contained in the acrylic polymer composition is volatilized in the supply section 6, and this volatile matter is introduced into the condenser 7 and connected to the condenser 7. The recovered solvent was stored in the storage tank 8.

The composition sprayed in the supply section 6 was continuously introduced into the barrel of the twin-screw kneader and kneaded.
FIG. 2 is a cross-sectional view schematically showing the structure inside the barrel of the twin-screw kneader used in this example. The supply part 6 is directly connected to the position shown in FIG. 2 inside the barrel, and the composition sprayed in the supply part 6 is kneaded with the kneading disk 21 from this position by the corrugated screw type feed screw 20 in the jacket part 22. The structure is such that it is sequentially guided to, and is agitated to renew the surface. 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 internal pressure of the barrel was kept at a vacuum of 50 Torr by the vacuum pump 9 connected to the condenser 7 for kneading. As a result, the composition in the barrel was surface-renewed and residual toluene and the like were volatilized, and this volatile substance was also introduced into the condenser 7 from the barrel and could be recovered in the recovery solvent storage tank 8. Here, in the stirring section in the barrel, the filling rate of the composition may be 95% or less so that the volatile gas flows well. The acrylic resin from which the volatile components were removed in this manner was discharged at about 140 ° C. from the nozzle portion 11 at the tip of the biaxial 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 WP1AL01 made of Daido Metal for resin.
The cooling bag 13 was filled through the 3 type 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. was used to make a bag with a heat sealing machine. The time when the set weight was filled was sensed by the weight measuring device installed under the cooling bag 13, and the mouth of the cooling bag 13 was sealed by the heat sealing machine 15 at that time. In this step, from the viewpoint of heat dissipation measures, the position of the nozzle portion 11, the position of the pump 12, and the position of filling the cooling bag 13 should be close to each other. This sealed cooling bag 13 was subsequently dropped into a water tank 17 (water temperature = about 5 ° C. to 40 ° C.) located on the lower side thereof, and was conveyed by a conveyor 16 installed below the water tank 17 for cooling. From this example, it was confirmed that an acrylic resin containing almost no volatile components can be easily manufactured with a relatively small-scale facility with good handleability.

[0044]

As described above, according to the present invention, two steps of volatilization and separation, that is, the step of injecting the composition in the feed section of the twin-screw kneader and the step of kneading in the barrel are specified under specific conditions. By doing so, the treated product can be handled easily and can be easily carried out by a small-scale facility, and even if it contains a large amount of volatile components, this is efficient and sufficient (1% by weight or less).
Thus, the acrylic resin removed can be obtained.

Furthermore, as described above, if the bag is filled with heat resistance and is 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 will be possible.

[Brief description of drawings]

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

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

[Explanation of symbols]

 1 Polymerization kettle 2 Pump 3 Heat exchanger 4 Pore 5 Twin-screw kneader 6 Twin-screw kneader supply part 7 Condenser 8 Recovery solvent storage tank 9 Vacuum pump 11 Nozzle part at the end of kneader 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 Feeding Screw 21 Kneading Disc 22 Jacket Section

Claims (2)

[Claims] 1. A method for producing an acrylic resin by removing the volatile component from an acrylic polymer composition containing 15 to 85% by weight of the volatile component, wherein the polymer composition is 1 kg / cm 2. ² or more pressure and 6
The volatile components are volatilized and removed by directly spraying into the feed section of a twin-screw kneader having an internal pressure of 400 Torr or less through pores or narrow gaps at a temperature of 0 ° C. to 220 ° C., and further the two-screw kneader. And 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 does not fill the barrel to remove residual volatile components. Manufacturing method. 2. A bag made of a resin film having a heat resistance of 110 ° C. or higher is filled with the acrylic resin from which residual volatile components have been removed by kneading with a biaxial kneader, and the bag is hermetically sealed. The bag of 40 is put into a cooling liquid of 40 ° C. or lower and moved, and / or the bag after the sealing is put to 40 ° C.
The method for producing an acrylic resin according to claim 1, further comprising a step of continuously cooling by moving in an atmosphere of a cooling liquid at a temperature of not higher than 0 ° C.