JPS6241523B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an acrylic acid alkyl ester polymer.

Conventionally, emulsion or suspension polymerization methods, solution polymerization methods, and bulk polymerization methods are known as methods for radical polymerization of ethylenically unsaturated monomers. Among these methods, emulsion or suspension polymerization methods have the disadvantage that emulsifiers and dispersants are mixed into the polymer, making it difficult to obtain pure products.
It takes a lot of man-hours and costs are high. In addition, the solution polymerization method is not free from environmental health problems and cost problems due to the use of large amounts of organic solvents, and also tends to cause the same problems as the emulsion or suspension polymerization method when removing the polymerized product. .

On the other hand, the bulk polymerization method does not have the above-mentioned problems and can be said to be an industrially advantageous method, but on the other hand, it is difficult to control the temperature due to the thickening caused by the rapid reaction progress depending on the type of monomer, and the reaction is slow. Easy to get out of control. As a result, not only is the polymerization work dangerous, but it is also difficult to design the molecular weight of the polymer, gelled products and degraded products are likely to occur as by-products, it is difficult to obtain a homogeneous polymer, and it is difficult to obtain a homogeneous polymer in the next step. Processing problems may occur.

Among ethylenically unsaturated monomers, styrene and the like are known to be able to control relatively high conversion rates, and their bulk polymerization has been studied and industrialized for a long time. Most of it is polymerized in a kettle-type prepolymerization vessel to a conversion rate of 30 to 70%, and the remainder is demonomerized to make the product.
Alternatively, the above-mentioned conversion rate is fed to an extruder and the reaction is carried out in a gentle manner up to a conversion rate of 95 to 96%.

On the other hand, acrylic acid alkyl ester monomers generate a large amount of heat during polymerization, and even when using a pot-based polymerization method such as the above-mentioned styrene, it is difficult to control the temperature, and the above-mentioned drawbacks due to runaway reactions cannot be avoided. For this reason, the reality is that industrial bulk polymerization methods for acrylic acid alkyl ester monomers have not yet been put to practical use.

The inventors have been conducting research on the bulk polymerization method of such acrylic acid alkyl ester monomers for many years, but in the course of their research, they were able to solve the problem during polymerization, which is a factor that inhibits the application of the bulk polymerization method mentioned above. By taking advantage of the rapid viscosity that accompanies a large calorific value, we have investigated a method for continuously obtaining homogeneous bulk polymers with optionally modified properties, and have achieved this invention.

That is, the present invention includes means for continuously transferring the contents continuously supplied from the main raw material supply port to the takeout port while renewing the surface thereof, and a temperature control mechanism over the entire transfer process, and a temperature control mechanism that covers the entire transfer process. A reactor consisting of a single-screw or twin-screw extruder having at least one auxiliary raw material supply port is used to produce an acrylic material containing an acrylic acid alkyl ester in a proportion of 50% by weight or more based on the total monomers from the main raw material supply port. A bulk polymerization raw material mainly consisting of acid alkyl ester monomers (hereinafter referred to as acrylic monomers) having a viscosity of 10 poise or less at room temperature is continuously supplied, and the temperature is increased to 100°C within the first half of the above transfer process.
The viscosity is increased by rapid polymerization at the following temperature, and the polymerization proceeds to a predetermined conversion rate at a temperature of 150°C or less in the following region, and the polymerization raw material mainly consisting of addition polymerization monomers is supplied from the auxiliary raw material supply port. An acrylic alkyl ester polymer characterized by continuously producing a bulk polymer in which an addition polymerization monomer is added to an acrylic alkyl ester polymer by continuously supplying the polymer and reacting at a temperature of 150°C or lower. (hereinafter referred to as acrylic polymer).

The drawing shows the cross-sectional structure of a single-screw extruder, which is an example of the above-mentioned reactor, and the method for producing an acrylic polymer of the present invention will be explained below with reference to this drawing.

In the figure, reference numeral 1 denotes a barrel constituting the outer cylinder of the extruder, with a main raw material supply port 2 at one end, a polymerization contents takeout port 3 at the other end, and an auxiliary raw material supply port 4 at the middle part.
is provided. Inside the barrel 1, a plurality of screws 6 are formed around a rotating shaft center 5.
The polymerization raw material supplied from the main raw material supply port 2 is mixed by the screw 6 by rotation of the shaft center 5, and is advanced while renewing the surface. screw 6 and barrel 1
The distance between the two is appropriately set in order to improve miscibility, but generally about 0.5 to 2 mm is appropriate.
7, 8, 9, 10, 11 are heating controllers provided at each part of the entire length of the barrel 1, and the corresponding areas a ₁ , a ₂ ,
Although the configuration is such that a ₃ , b ₁ , and b ₂ can each be independently controlled to a predetermined temperature, the configuration may be such that the heating is controlled uniformly over the entire length of the barrel 1. Also,
The type, number, and spacing of heating controllers can also be set depending on desired reaction conditions.

A raw material for bulk polymerization containing mainly acrylic monomer and having a viscosity of 10 poise or less at room temperature is continuously fed into this extruder from the supply port 2 at a constant rate. The supplied raw materials are mixed by the rotation of the screw 6 and transferred while the surface is renewed. At this time, the temperature is gradually increased in the region a 1 using the heating controller 7, for example, so that the viscosity increases due to rapid polymerization in the first half region indicated by a in the figure during the transfer process from the supply port 2 to the take-out port ₃ . The temperature is controlled by the heating controller 8 so that polymerization starts instantaneously in area _a2 and the bulk polymerization reaction rapidly proceeds. The polymerized contents thickened in this way advance while being further mixed and surface renewed to continue polymerization, and pass through the temperature-controlled area _a3 by the heating controller 9 to a predetermined conversion rate, for example, the reaction is almost completed. At this point, a polymerization raw material mainly consisting of monomers for addition polymerization is supplied from the auxiliary raw material supply port 4, and while being mixed and surface renewed in the same way, the temperature is controlled by heating controllers 10 and 11. area
An addition polymerization reaction takes place during the steps b ₁ and b ₂ , and finally a bulk polymer consisting of an acrylic polymer to which the monomer for addition polymerization has been added is continuously produced from the outlet 3 at the open end.

In this example, the axis 5 of the single screw 6 is coaxial between the screws 6, 6, but for the purpose of reaction control, the barrel 1 is configured so that its diameter differs in each part. The amount of content transferred may be varied.

Further, in the above example, a single-screw extruder is used, but polymerization can be carried out using a twin-screw extruder in the same manner as above. In the case of a two-axis screw, each axis can be rotated in the same direction or in different directions. In these screw extruders, as mentioned earlier, the distance between the screw and the barrel is preferably set to about 0.5 to 2 mm, but the speed gradient, that is, [pi (π) × rotation speed × Screw outer diameter/gap between barrel and screw] is generally 1000/min or more.

In the above method, it is very important to rapidly advance the polymerization reaction in the first half of the transfer process in the barrel to increase the viscosity of the polymerized content. This is a requirement to enable control. That is, in the reactor used in this invention, such as the above-mentioned screw extruder, it is extremely easy to stably transport materials with a constant viscosity, but if the reactor has a large viscosity gradient in the barrel length direction and the low viscosity region is long, For example, the screw in the above-mentioned screw extruder becomes partially idle in the low viscosity region, causing stagnation or backflow of the contents, making stable transfer difficult. For this reason, it is important to maintain a state in which the viscosity gradient is small over as long a region as possible during the transfer process.

As mentioned above, acrylic monomers tend to thicken due to the rapid progress of the polymerization reaction, and this has hitherto been an obstacle to the application of bulk polymerization, but in the present invention, this property is used to the contrary. That is,
The viscosity of polymerization raw materials mainly made of acrylic monomers is
Even if the viscosity is less than 10 poise, the viscosity can be increased to the extent necessary for stable transfer in just a few minutes by rapid polymerization in at least the first half of the transfer process. Moreover, in the method of this invention, it is possible to control the temperature according to subdivided areas during the transfer process, and the surface of the contents is transferred while being renewed, so that the contact surface between the contents and the reactor wall is constantly renewed. Since heat exchange between the two is performed efficiently and the temperature distribution width of the contents is narrowed, it is possible to sufficiently control side reactions and runaway reactions so as not to occur. For these reasons, bulk polymerization of acrylic monomers, which has been considered difficult in the past, can be produced in a continuous manner, which has not been possible with other ethylenic monomers.

The viscosity required for the above-mentioned stable transfer varies depending on the type and size of the reactor, the type of acrylic monomer, the transfer rate of the polymerized contents, the properties of the desired bulk polymer, etc., but is generally 100~ It is in the range of several 1000 poise. Furthermore, although the region in which rapid polymerization is carried out is the _a2 region in the first half region a of the transfer process in the above example, it goes without saying that it may be an earlier region, such as the _a1 region in the above example.

In addition, in the conventional pot-type solution polymerization method of acrylic monomers, which is controlled by organic solvent dilution, it generally takes a long time of 1 to 10 hours to achieve the conversion rate that provides the above-mentioned required viscosity.

The polymerization raw material mainly composed of acrylic monomers used in this invention contains acrylic acid alkyl ester in a proportion of 50% or more by weight based on the total monomers, and if necessary, methacrylic acid alkyl ester and acrylic acid that can be copolymerized with this. It is a mixture of monomers using various ethylenically unsaturated monomers such as , methacrylic acid, maleic acid, styrene, vinyl acetate, and acrylonitrile, with the addition of a radical polymerization catalyst and, if necessary, a molecular weight regulator. It is a liquid agent with the following viscosity.

Examples of the above radical polymerization catalyst include organic peroxides such as benzoyl peroxide, cumene hydroperoxide, di-t-butyl peroxide, and lauroyl peroxide, and azo compounds such as azobisisobutyronitrile. Can be used. These catalyst amounts are monomer
It is generally about 0.01 to 1 part by weight per 100 parts by weight. In addition to the above catalysts, it is also possible to use redox catalysts that can generate radicals at low temperatures.
As the molecular weight regulator, a chain transfer agent such as thioglycol, thioglycolic acid, butyl mercaptan, lauryl mercaptan, and decyl mercaptan is used.

The radical polymerization catalyst and the molecular weight regulator may not be mixed with the monomers from the beginning, but may be added to the monomers alone and then reacted with the monomers.
For example, they can be introduced by providing a suitable feed port at a desired location in region a of the barrel of the single screw extruder shown. 12 in the figure is a supply port provided at the part where the axis 5 of the screw 6 on the front stage side of area _a2 is tapered, and 13 is a supply port for introducing by-products or arbitrary additives in the polymerization reaction. This is an exhaust port for low-molecular volatile substances generated as a result.

On the other hand, the polymerization raw material mainly composed of monomers for addition polymerization is used to modify the properties of the polymer made of the polymerization raw material mainly composed of the acrylic monomer, and is capable of addition polymerization to the above-mentioned polymer. Any monomer component can be used. Examples of modifying the properties of polymers include, for example, imparting hydrophilicity to polymers, and improving the elasticity of polymers and cohesive force when used as adhesives. Monomer components that are themselves hydrophilic or capable of providing water-soluble polymers are used, and in the latter case monomer components that themselves have a high glass transition temperature (e.g.
300〓 or more) Monomer components that can give a polymer are used.

In this way, the type and amount of polymerization raw materials mainly consisting of monomers for addition polymerization can be selected according to the intended use of the bulk polymer, and other components such as polymerization catalysts can also be selected according to the above. You just have to decide. In addition, it goes without saying that two or more of these may be used in combination, and it is also possible to provide desired characteristics by providing a plurality of sub-material supply ports in the reactor and performing addition polymerization in stages. .

In addition, in this invention, in order to impart appropriate properties to the produced bulk polymer, if desired, a small amount of solvent,
Plasticizers, polymers, etc. may be blended into the raw materials. This compounding amount is the total amount of these components, including all monomers.
It is desirable that the amount is 25 parts by weight or less per 100 parts by weight.

In addition, it is desirable that the above-mentioned raw materials for bulk polymerization and raw materials for addition polymerization mainly composed of acrylic monomers be subjected to nitrogen gas purging treatment to remove dissolved oxygen in order to increase reactivity when used. This nitrogen gas replacement may be performed on the raw material liquid in advance, or may be performed by providing a supply port in an appropriate portion of the reactor and blowing nitrogen gas into the reactor.

In the continuous polymerization method described above, the heating temperature in each part of the reactor is appropriately controlled depending on the type of monomer and polymerization catalyst used, the amount of polymerization contents transferred to each part, etc. It is desirable to adjust the temperature of the polymerized contents within a range of 40 to 150°C. In particular, the heating temperature in the area where the viscosity is increased by rapid polymerization should be set at a temperature of 100° C. or lower depending on the type and amount of the polymerization catalyst, the structure of the reactor, and the transfer conditions.
Incidentally, the conversion rate of the bulk polymer obtained by the method of this invention is usually 93 to 99% by weight.

As detailed above, according to the present invention, it is possible to perform bulk polymerization of acrylic monomers, which was previously considered impossible, and to achieve high quality polymerization with a relatively small and homogeneous molecular weight distribution and no gelled or degraded products. Furthermore, the outstanding effect of being able to continuously produce bulk polymers with desired properties is achieved.

Next, examples of this invention will be described. In the following, parts and % mean parts by weight and % by weight, respectively.

Example 1 As a reactor, screw outer diameter is 40 mm, barrel length is 1250 mm, and gap between barrel and screw peak is 1 mm.
The interior is divided into five zones A, B, C, D, and E from the front end side, and each zone can be independently temperature controlled, and the A and D zones have a supply port on the front end side. Using an axial screw extruder, the speed gradient was 5024/min, and the set temperature of each zone was A,
B, C, D, E = 80℃, 100℃, 120℃, 120℃,
The temperature was 120℃.

A mixture of 85 parts of butyl acrylate, 15 parts of acrylonitrile, 3 parts of 2-hydroxyethyl acrylate, and 0.15 parts of azobisisobutyronitrile with a viscosity at room temperature was added to the feed port of the A zone of this reactor.
The polymerization raw material liquid of 0.8 centipoise was replaced with nitrogen gas in advance and then continuously supplied at a rate of 50 g/min, and methyl methacrylate was added to the supply port of the D zone.
A polymerization raw material solution consisting of 100 parts and 0.6 parts of benzoyl peroxide was replaced with nitrogen gas in advance, and
The reaction was carried out by continuously feeding at a rate of g/min.

The bulk polymer obtained continuously by this method has a polymer conversion rate of 97.5% and a weight average molecular weight (w) =
516,000, number average molecular weight (n) = 39,000, w/
n=13.2. In addition, this bulk polymer was heat-pressed into a 1 mm thick sheet, and the physical properties of this sheet were measured from a stress-strain curve. As a result, the elastic modulus was 19.8 kg/
^cm2 , 100% modulus 14.8Kg/ ^cm2 , breaking strength 40
Kg/cm ² and elongation was 900%. This shows that the above bulk polymer can be suitably used as an acrylic acid alkyl ester-based elastic material.

On the other hand, the bulk polymer obtained only by supplying from the supply port of the A zone (polymer conversion rate 97.9%, w58
As a result of investigating the same sheet characteristics as above for
Elastic modulus 2.5Kg/cm ² , 100% modulus 2.3Kg/cm ² ,
The breaking strength was 2.7 Kg/cm ² and the elongation was 1830%.

Example 2 Screw outer diameter 50mm, barrel length as reactor
1250mm, with a gap of 1mm between the barrel and the screw mountain,
A twin-shaft screw whose interior is divided into five zones A, B, C, D, and E from the front end, each zone can be temperature controlled independently, and has a supply port at the front end of zones A and D. Using an extruder, the speed gradient is 7850/min, and the set temperature of each zone is A, B,
C, D, E = 100℃, 100℃, 100℃, 120℃, 150
℃.

A polymerization raw material solution with a viscosity of 0.8 centipoise at room temperature consisting of 70 parts of butyl acrylate, 30 parts of acrylonitrile, 5 parts of acrylic acid, and 0.1 part of azobisisobutyronitrile was placed in advance in the supply port of the A zone of the above reactor under nitrogen. After purging with gas, the polymerization raw material solution consisting of 100 parts of acrylic acid and 0.2 parts of benzoyl peroxide is supplied continuously from the supply port of the D zone at a rate of 50 g/min, and the gas is purged with nitrogen gas beforehand, and then being supplied at a rate of 50 g/min. The reaction was carried out by continuously feeding at a rate of .

The bulk polymer obtained continuously by this method had a polymer conversion rate of 98.1%, w = 450,000, and n = 5.29.
10,000, w/n=8.5. In addition, the carboxyl group contained in this bulk polymer
After neutralizing with 0.1 equivalent of caustic soda to form a salt, it was immersed in water at 25°C for 24 hours to determine its swelling ratio and dissolved content.

In addition, each characteristic is based on the following formula, where the initial weight (before immersion) is W, the swelling weight after immersion is _W1 , and the dry weight after drying at 100℃ for 5 hours after immersion is _W2 . This is the calculated value.

Swelling rate (%) = [(W ₁ - W) / W] × 100 Dissolved content (%) = [(W - W ₂ ) / W] × 100 The result is that the swelling rate is 320% and the dissolved content is 5%. It was hot. This shows that the above bulk polymer can be suitably used as a water-swellable material.

On the other hand, the bulk polymer obtained only by supplying from the supply port of the A zone (polymer conversion rate 99.5%, w =
400,000), the results were as follows:
The swelling rate was 10% and the dissolved content was 2%.

Example 3 Using the same reactor as Example 1, the set temperatures of each zone were A, B, C, D, E = 100°C, 100°C,
The temperature was 120℃, 120℃, 120℃, and the velocity gradient was the same.

80 parts of butyl acrylate and 20 parts of 2-ethylhexyl acrylate were added to the supply port of zone A of this reactor.
A polymerization raw material solution with a viscosity of 0.9 centipoise at room temperature consisting of 5 parts of acrylic acid and 0.2 parts of azobisisobutyronitrile was replaced with nitrogen gas in advance.
At the same time, a polymerization raw material solution consisting of 100 parts of methyl methacrylate and 0.5 parts of benzoyl peroxide was continuously supplied at a rate of 15 g/min to the supply port of the D zone after being replaced with nitrogen gas in advance. and reacted.

The bulk polymer continuously extracted by this method has a polymer conversion rate of 98.9%, w 451,000, n 5.34
1,000, w/n = 8.45. In addition, this bulk polymer was dissolved in toluene to prepare a 30% toluene solution, and this was applied to a 25μ thick polyester film.
The adhesive properties of the adhesive tape obtained by applying it to a thickness of 25 μm were investigated, and the adhesive strength was 850 g/20 mm, and the holding power was over 1000 minutes.

The above adhesive strength is based on JIS-Z-1528.
The adhesive strength was measured after 180 degree peeling, and the retention strength was measured using adhesive tape (25 mm x
25mm) was attached and a load of 1 kg was applied at 40°C, and the time taken for it to fall was measured. As is clear from the above test results, it can be seen that the bulk polymers of the above examples provide adhesives with excellent adhesive strength and cohesive strength.

On the other hand, the bulk polymer obtained only by supplying from the supply port of the A zone (polymer conversion rate 99.1%, w54
The same test as above was carried out for 1,000 yen), and the results were that the adhesive force was 550 g/20 mm and the holding force was 45 minutes.

[Brief explanation of the drawing]

The drawing is a sectional view of a single-screw extruder shown as an example of a reactor used in the present invention.

Claims (1)

[Claims] 1. A means for continuously transporting the contents continuously supplied from the main raw material supply port to the take-out port while renewing the surface, and a temperature control mechanism over the entire transfer process, and at least one sub-container in the middle of the transfer process. An acrylic acid alkyl ester monomer containing an acrylic acid alkyl ester in a proportion of 50% by weight or more based on the total monomers from the main raw material supply port using a reactor consisting of a single or twin screw extruder having a raw material supply port. Continuously supplies raw materials for bulk polymerization that have a viscosity of 10 poise or less at room temperature, mainly consisting of
The viscosity is increased by rapid polymerization at a temperature of 100℃ or less in the first half of the above transfer process, and then in the subsequent region.
Polymerization is allowed to proceed to a predetermined conversion rate at a temperature of 150°C or less, and polymerization raw materials mainly consisting of addition polymerization monomers are continuously supplied from the auxiliary raw material supply port to 150 °C.
A method for producing an acrylic alkyl ester polymer, which comprises continuously producing a bulk polymer in which an addition polymerization monomer is added to an acrylic alkyl ester polymer by reacting at a temperature of 0.degree. C. or lower.