JPH11255828A - Preparation of methacrylic polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preparing methacrylic polymers excellent in thermal decomposition resistance and molding processability with good productivity. SOLUTION: In a method for preparing a methacrylic polymer by the process comprising a continuous bulk polymerization step, a monomer comprising (a) 0.01-1.0 mol.% mercaptan and (b) a radical polymerization initiator in an amount satisfying formula (1a): 1.3<=A.(B<-2/5> )×10<5> ; formula (2): A<=0.5×10<-4> ; and formula (3a): 0.01<=B<=0.3 [wherein A is a number of mol of the radical polymerization initiator in 1 mol monomer supplied; and B is a half-life (hr) of the radical polymerization initiator at the polymerization temperature] is continuously supplied to a reaction zone to conduct polymerization in the polymerization temperature range of from 110 deg.C to lower than 150 deg.C such that the rate of polymerization ϕ (wt.%) satisfies formula (4): 40<=ϕ<=65, and the reaction mixture is continuously taken out of this reaction zone.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for continuously producing a methacrylic polymer by bulk polymerization.

[0002]

2. Description of the Related Art Conventional polymethyl methacrylate (PM)
The industrial process for MA) was a batch polymerization process using a suspension polymerization process. This method is a suitable production method for high-mix low-volume production.However, since auxiliary agents such as dispersants are used, they remain in the molding material and deteriorate the quality, and a large amount of Requires water washing and subsequent drying. Furthermore, since the polymerization operation is of a batch type, the operation operation is inefficient and complicated, and at the same time, the required costs such as equipment costs and operation costs are high. Furthermore, at the present time when pollution control is becoming strict, it is not preferable to discharge a large amount of water or washing water used for polymerization containing auxiliary agents such as dispersants and unreacted monomers. If a processing device is to be provided, the required cost will further increase, and the manufacturing method must be industrially disadvantageous. In order to solve the problems of the suspension polymerization method, a method of continuously producing MMA by bulk polymerization has been proposed.

For example, Japanese Patent Publication No. 52-32665 discloses a method in which the half-life and the amount of a radical initiator to be added at a polymerization temperature are specified, and a monomer conversion rate is from 50% to 78% at a polymerization reaction temperature of 130 ° C. to 160 ° C. Is disclosed. In fact, according to this method, it was possible to produce a methacrylic polymer molding material having excellent heat resistance and excellent thermal decomposability during molding and having a wide molding temperature range. However, in the range of the amount of the radical initiator added in this method, it is necessary to increase the residence time in the reaction zone in order to stably control the polymerization and perform the operation, so that the polymer production amount per unit volume and unit time is reduced. There was little demand for further improvement in productivity.

Japanese Patent Application Laid-Open No. 3-111408 discloses that a monomer mixture containing methyl methacrylate as a main component can be used as a radical initiator in a half-life at a polymerization temperature of 0.5 to 0.5 with a single complete mixing reactor. The average residence time is 1/200 to 1 / 10,000 in terms of the ratio to the half-life of the radical initiator while stirring with a stirrer having a stirring power of 0.5 to 20 kW per 1 m ^{3 of} the reaction solution using a solution of 120 seconds. And a method for producing a methacrylic polymer that is polymerized at a temperature of 130 to 160 ° C. at a monomer conversion of 45 to 70 wt%.

In Japanese Patent Application Laid-Open No. Hei 7-126308, a monomer containing methyl methacrylate as a main component is subjected to bulk polymerization using a complete mixing type reaction tank, and a polymer content of 40 is obtained.
% To 70 wt%, the reactor is filled with no gas phase, and the polymerization temperature is 120 ° C. to 180 ° C.
A method for producing a methacrylic polymer in which the average stay time is 15 minutes to 2 hours, and a radical initiator having a half-life at the polymerization temperature of 1 minute or less is used, and the polymerization is carried out under the prescribed amount. It is shown.

[0006] In JP-A-3-111408 and JP-A-7-126308, the use of a radical initiator having a very short half-life at the polymerization temperature makes it possible to easily control the polymerization reaction. There is.
However, since the amount of addition is large, the polymer contains a large amount of terminal double bonds due to a radical disproportionation termination reaction. As described above, when there are many terminal double bonds, thermal decomposition is liable to occur, and there has been a problem that heat resistance has to be sacrificed in order to widen a molding temperature range which is an index of moldability.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of such conventional problems, and is intended to produce a methacrylic polymer having excellent heat decomposition resistance and excellent moldability with high productivity. The purpose is to provide a way to:

[0008]

SUMMARY OF THE INVENTION The present invention provides a continuous bulk polymerization of a methacrylic polymer containing 80% by weight or more of methyl methacrylate units and 20% by weight or less of alkyl acrylate or alkyl methacrylate (excluding methyl methacrylate) units. In the method for producing by the steps including the steps, (a) 0.01 to 1.0 mol% of mercaptan, and (b) the following formulas (1a), (2) and (3)
Amount of radical polymerization initiator satisfying a) 1.3 ≦ A · (B ^−2/5 ) × 10 ⁵ (1a) A ≦ 0.5 × 10 ⁻⁴ (2) 0.01 ≦ B ≦ 0. 3 (3a) A monomer containing (A is the number of moles of the radical polymerization initiator in 1 mole of the supplied monomer and B is a half-life (hr) at the polymerization temperature of the radical polymerization initiator) is continuously formed in the reaction zone. The reaction mixture in the reaction zone was heated to 110 ° C.
The mixture is substantially uniformly stirred and mixed at a temperature in the range of less than 150 ° C., and the polymer content (% by weight) φ in the reaction mixture in this reaction zone satisfies the following formula: 40 ≦ φ ≦ 65 (4) The present invention relates to a method for producing a methacrylic polymer, which comprises carrying out polymerization in such a manner and continuously taking out a reaction mixture from the reaction zone.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A methacrylic polymer obtained by the method of the present invention is a polymer containing not less than 80% by weight of methyl methacrylate units and not more than 20% by weight of alkyl acrylate or alkyl methacrylate (excluding methyl methacrylate) units. It is a union and includes both a homopolymer and a copolymer of methyl methacrylate.
Each is obtained by homopolymerization using methyl methacrylate alone as a monomer or copolymerization using methyl methacrylate and alkyl acrylate or alkyl methacrylate (excluding methyl methacrylate) as monomers. The alkyl acrylate used together with methyl methacrylate in the case of copolymerization is selected from those having an alkyl group having 1 to 18 carbon atoms, such as methyl, ethyl, n-propyl, n-butyl, 2-
Alkyl acrylates having an alkyl group such as ethylhexyl, dodecyl, stearyl and the like are included.

The alkyl methacrylate used together with methyl methacrylate in the copolymerization is selected from those having an alkyl group having 2 to 18 carbon atoms. For example, the alkyl methacrylate having the same alkyl group as described above except for the methyl group is used. Is included.

The methacrylic polymer obtained by the present invention is particularly preferably a homopolymer, that is, polymethyl methacrylate, or a copolymer of methyl methacrylate with an alkyl acrylate selected from methyl, ethyl, and butyl acrylate.

Methyl methacrylate has a different polymerization activity from other alkyl methacrylates and alkyl acrylates to be copolymerized with it. Therefore, when trying to obtain a copolymer having the above composition, the composition of the charged monomer mixture depends on their polymerization activity. It is appropriately selected depending on it. For example, when methyl methacrylate is copolymerized with methyl acrylate or ethyl acrylate, the composition of the charged monomer mixture is about 70 wt% or more of methyl methacrylate and about 30 wt% or less of methyl acrylate or ethyl acrylate.

In the present invention, a monomer mixture containing mercaptan and methyl methacrylate containing a radical polymerization initiator as a main component is continuously supplied to one reaction zone.

The mercaptans used in the present invention include, for example, n-butyl, isobutyl, n-octyl and n-butyl.
-Dodecyl, sec-butyl, sec-dodecyl, te
primary, secondary and tertiary mercaptans having an alkyl or substituted alkyl group such as rtbutyl mercaptan;
For example, phenylmercaptan, thiocresol, 4-t
aromatic mercaptans such as tert-butyl-O-thiocresol; thioglycolic acid and its esters; and mercaptans having 3 to 18 carbon atoms such as ethylenethioglycol. These can be used alone or in combination of two or more. Among these mercaptans, t
tert-butyl, n-butyl, n-octyl, n-dodecyl mercaptan are preferred.

If the amount of the mercaptan used is too small, the reaction rate may be abnormally increased and control may be difficult.
It is difficult to obtain a polymer having a constant quality and excellent moldability. On the other hand, if the amount is too large, the degree of polymerization is reduced and the product strength is reduced.
It is from 0.01 to 1.0 mol%, preferably from 0.01 to 0.05 mol%.

The amount of the radical polymerization initiator used in the present invention and the amount of the radical polymerization initiator in the monomer supplied to the reaction zone are as follows: A is the number of moles of the radical polymerization initiator in 1 mol of the supplied monomer, and B is the radical polymerization initiator. When the half life (hr) at the polymerization temperature of the agent is represented by A and B, the formula (1)
a), (2) and (3a) must be satisfied.

1.3 ≦ A · (B ^−2/5 ) × 10 ⁵ (1a) A ≦ 0.5 × 10 ⁻⁴ (2) 0.01 ≦ B ≦ 0.3 (3a) Further, A and B represents the formula (1b), (2) and (3)
Preferably, b) is satisfied.

10 <(A / B) ^1/2 × 10 ³ (1b) A ≦ 0.5 × 10 ⁻⁴ (2) 0.034 ≦ B ≦ 0.3 (3b) Range of the formula (1a) If the ratio exceeds the above range, the production amount of the polymer per unit volume / time will be low, and the object of the present invention cannot be achieved. More preferably, the range of the expression (1b) is desirable. When the value exceeds the range of the expression (2),
As the thermal decomposition resistance of the polymer decreases, it becomes difficult to control the polymerization reaction. Further, when the value exceeds the lower limit of the formula (3a), the amount of the radical initiator used increases, so that the thermal decomposition resistance decreases. On the other hand, when the value exceeds the upper limit of the formula (3a), it is necessary to lengthen the residence time in the reaction zone in order to stably control the polymerization reaction, so that the productivity per unit volume / unit time is reduced. Further, the range of the formula (3b) is preferable for improving the thermal decomposition resistance. The range of the radical initiator half-life and the concentration used determined by the formulas (1a), (2) and (3a), and the formulas (1b), (2) and (3)
FIG. 1 shows the range of the radical initiator half-life and the concentration used determined by b). FIG. 2 shows the range of the half-life of the radical initiator and the range of the concentration used in the claims of each prior art. However, all of them show only the half-life and the concentration used, and do not show all conditions of the present invention and the prior art.

In the present invention, as the value of "half-life at the polymerization temperature of the radical polymerization initiator", a value described in a known product catalog such as NOF Corporation or Wako Pure Chemical Industries, Ltd. was used. The radical polymerization initiator used in the present invention can be used as long as it satisfies the above formula (3a), preferably (3b) at the polymerization temperature.
Butylperoxy-3,5,5-trimethylhexanate, tert-butylperoxylaurate, tert
-Butyl peroxyisopropyl monocarbonate, t
tert-hexylperoxyisopropyl monocarbonate, tert-butylperoxyacetate, 1,1
-Bis (tert-butylperoxy) 3,3,5-trimethylcyclohexane, tert-butylperoxy-2-ethylhexanate, tert-butylperoxyisobutyrate, tert-hexyl-hexylperoxy-2-ethylhexanate Or an organic peroxide such as 2- (carbamoylazo) -isobutyronitrile;
1′-azobis (1-cyclohexanecarbonitrile,
2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), dimethyl 2,
It can be selected from azo compounds such as 2'-azobisisobutyrate in consideration of the polymerization temperature.

These radical initiators may be used alone or in combination of two or more.
When two or more types are used, the polymerization becomes complicated, and thus one type is preferably used alone. When two or more initiators are used, the half-life of each initiator is selected so as to satisfy the above relational expression, and the half-life of the initiator having the shortest half-life and the total molar concentration of the initiator are as described above. The concentration is selected so as to fall within the range satisfying the relational expression.

According to the present invention, in addition to the use of the initiator having a predetermined half-life at a predetermined concentration, by satisfying the following conditions, a more excellent effect as compared with the conventional method can be obtained. Show.

First, in the present invention, it is extremely important that the whole reaction mixture supplied to the reaction zone is substantially uniformly stirred and mixed at a certain temperature of 110 ° C. or more and less than 150 ° C. for polymerization. If the temperature of the reaction mixture is lower than 110 ° C., the viscosity becomes high, and it is difficult to achieve sufficient mixing or heat transfer, and it is difficult to stably control the reaction. Is called polymerization rate and wt%
To display. It is difficult to give. The higher the polymerization temperature, the lower the viscosity, which is advantageous in terms of reaction control.However, the generation of by-products such as methyl methacrylate dimer increases, and the heat resistance of the polymer and the reduction in molding processability are reduced. Accompany. The polymerization temperature is more preferably 120 ° C. or higher and 15
It is below 0 ° C.

Since heat is generated in the reaction zone due to the polymerization reaction and stirring and mixing, the heat is removed, and in some cases, the temperature is controlled by heating to a predetermined polymerization temperature. Temperature control can be performed by a known method. For example, heat transfer heat removal or heating by circulating a heat medium to a draft tube or a coil installed in a jacket, a reaction zone or the like, cooling supply of a monomer mixture,
A method such as reflux cooling can be employed.

Further, in the present invention, the polymer content φ of the reaction mixture in the reaction zone, that is, the polymerization rate, is set to a substantially constant value satisfying the following equation (4): 40 ≦ φ ≦ 65 (4) It is extremely important to maintain. When the polymerization rate φ exceeds the upper limit defined by the formula (4), it is difficult to sufficiently achieve mixing and heat transfer, and it becomes difficult to perform a stable operation. When the polymerization rate φ is equal to or less than the lower limit defined by the formula (4), the cost required for separating volatiles containing an unreacted monomer as a main component increases, and the industrial merit decreases. Therefore, it is necessary to maintain the polymerization rate φ within the range of the above equation (4).

The reactor used for carrying out the present invention is a tank-type reactor provided with a stirrer provided with a supply port and an outlet, and the stirrer must have mixing performance over the entire reaction zone. is there.

In the present invention, after such a polymerization step, a volatile matter separation step mainly comprising an unreacted monomer is usually provided, and a reaction mixture having a predetermined polymerization rate which is continuously fed is provided. Is heated to 200 to 290 ° C. under reduced pressure to continuously separate and remove most of the volatile substances mainly composed of monomers. When the residual monomer content in the final molding material is 1 w
t% or less, preferably 0.3 wt% or less.

When the methacrylic polymer thus produced is used as a molding material, higher alcohols,
Lubricants such as higher fatty acid esters can be added. Further, if necessary, an ultraviolet absorber, a heat stabilizer, a coloring agent, an antistatic agent and the like can be added.

The methacrylic polymer obtained in the present invention comprises:
When used as a molding material, it is characterized by being particularly excellent in molding workability in terms of quality. The quality of the moldability is determined by the temperature range in which the moldability is possible. The larger the width is, the better. The lower limit temperature of this temperature range is mainly determined by the fluidity of the molding material, and can be relatively easily controlled by changing the average degree of polymerization, the amount of the copolymer component, and the amount of the plasticizer. However, increasing the fluidity and lowering the lower limit temperature causes a decrease in heat resistance, mechanical strength, and the like at the same time, so it is practically difficult to lower the lower limit temperature.

On the other hand, the upper limit of the above temperature range depends on the thermal decomposition resistance and volatile matter content of the molding material. The thermal decomposition resistance of the polymer is determined mainly by the number of double bonds at the polymer chain terminal due to the termination reaction of the polymer radical, and the copolymerization amount of the alkyl acrylate. Since the smaller the double bond, the better the thermal decomposition resistance, the smaller the amount of the radical initiator added, the better. The higher the copolymerization amount of the alkyl acrylate, the better the thermal decomposition resistance. However, if the copolymerization amount of the alkyl acrylate increases, the glass transition temperature of the copolymer decreases and the heat resistance decreases. Is required, the copolymerization amount is limited.

As described above, the lower limit of the moldable temperature range can be easily lowered by adjusting the degree of polymerization, the amount of the copolymerization component, the plasticizer to be blended, and the like. It has been an unsolved problem to obtain a polymer having excellent heat resistance and low volatile matter content with high productivity.

According to the present invention, a methacrylic polymer having excellent heat decomposition resistance and a high upper limit temperature at which molding can be performed is obtained, so that a molding material having a wide molding temperature range and excellent molding processability can be obtained. At the same time, improvement in productivity, which was a concern, can be expected.

[0032]

The present invention will be described in more detail with reference to the following examples, which do not limit the present invention.

The thermal decomposition resistance of the examples was evaluated using a differential thermal electronic balance (SSC50) manufactured by Seiko Denshi Kogyo KK.
0) shows the bending temperature (° C.) when the polymer pellets were heated to 400 ° C. in air at a rate of 5 ° C./min.

Example 1 0.15 mol% (0.22 wt%) of n-octyl mercaptan was used as a radical initiator with respect to a monomer mixture consisting of 98 wt% of purified methyl methacrylate and 2 wt% of methyl acrylate. A reaction in which a raw material monomer obtained by mixing butylperoxy-3,5,5-trimethylhexanoate 3.5 × 10 ^-5 mol / monomer 1 mol (0.0080 wt%) is stirred and mixed at a polymerization temperature of 135 ° C. The area was fed continuously.

The half life at the polymerization temperature is 0.24 hr. Polymerization was carried out with the average residence time in the reaction zone being 2.7 hours. The reaction mixture was continuously taken out of the reaction zone, and continuously supplied to a vent extruder-type extruder to separate and remove volatiles mainly composed of unreacted monomers to obtain a polymer.

When the physical properties of the polymer in each step were examined,
The polymer content in the reaction mixture after the polymerization reaction zone is 46 wt.
%, And the dimer content was as low as 0.04 wt%. The residual monomer ratio of the polymer obtained after separating the volatile components was 0.03% by weight, and the content of the dimer was 0.02% by weight or less. When the thermal decomposition resistance of this polymer was evaluated, the results shown in Table 1 were obtained, and the polymer was very excellent in thermal decomposition resistance. In addition, the amount of polymer produced per unit volume and unit time in this example is 170 kg.
/ Hr / m ³ , very high productivity was obtained. 3
Even in the continuous operation for 60 hours, there was no problem in controlling the polymerization, and no observation of the inside of the reaction tank after the completion of the operation showed any adhesion to the apparatus or generation of foreign matter.

Examples 2 to 6 Polymers having the physical properties shown in Table 2 were obtained in the same manner as in Example 1 except that the raw materials and conditions shown in Table 1 were used. 360 h in any of Examples 2 to 6
Even in the continuous operation of r, there was no problem in controlling the polymerization, and no observation of the inside of the reaction tank after the completion of the operation showed any adhesion to the apparatus or generation of foreign matter.

Comparative Example 1 A polymer having the physical properties shown in Table 2 was obtained in the same manner as in Example 1 except that the raw materials and conditions shown in Table 1 were used. From these results, it is clear that under these conditions, the polymer production per unit volume and per unit time is inferior, although the heat decomposition resistance is excellent. Comparative Examples 2 to 4 Polymers having the physical properties shown in Table 2 were obtained in the same manner as in Example 1 except that the raw materials and conditions shown in Table 1 were used. From these results, it is clear that under these conditions, the thermal decomposition resistance is poor.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

According to the present invention, when a monomer mixture containing methyl methacrylate as a main component is subjected to continuous bulk polymerization using a complete mixing type reaction tank, the production volume per unit volume and unit time is large, and the productivity is high. Although it is high, the polymerization reaction can be controlled stably, and a methacrylic polymer having excellent heat-decomposability and good moldability can be produced.

[Brief description of the drawings]

FIG. 1 is a diagram showing the range of the number of moles of a radical polymerization initiator per mole of a supplied monomer (A) and the half life (B) of the radical polymerization initiator at a polymerization temperature in the present invention.

FIG. 2 is a diagram showing the range of the number of moles of a radical polymerization initiator per mole of a supplied monomer (A) and the half-life at the polymerization temperature of the radical polymerization initiator (B) in the prior art.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Shigeaki Sasaki 3 Kaigan-dori, Toyama City, Toyama Prefecture Mitsubishi Rayon Co., Ltd. Toyama Works (72) Inventor Koji Ishizaka 3 Kaigan-dori, Toyama City, Toyama Prefecture Mitsubishi Rayon Co., Ltd. In-house (72) Inventor Takeshi Kitayama 3 Kaigan-dori, Toyama City, Toyama Prefecture Mitsubishi Rayon Co., Ltd. Toyama Office (72) Inventor Tatsuyuki Takayanagi 3 Kaigan-dori, Toyama City, Toyama Prefecture Mitsubishi Rayon Co., Ltd. Toyama Office

Claims (2)

[Claims] 1. 80% by weight or more of methyl methacrylate units and 20% by weight or less of alkyl acrylate or alkyl methacrylate (excluding methyl methacrylate)
(A) 0.01 to 1.0 mol% of a mercaptan, and (b) a compound represented by the following formula (1):
a) Radical polymerization initiator in an amount satisfying (2) and (3a) 1.3 ≦ A · (B ^−2/5 ) × 10 ⁵ (1a) A ≦ 0.5 × 10 ⁻⁴ (2) 0.01 ≦ B ≦ 0.3 (3a) (A is the number of moles of the radical polymerization initiator in 1 mole of the supplied monomer, and B is the half-life (hr) of the radical polymerization initiator at the polymerization temperature.) Is continuously supplied to the reaction zone, and the reaction mixture in the reaction zone is substantially uniformly stirred and mixed at a certain temperature in the range of 110 ° C. to less than 150 ° C. Polymerization is carried out so that the polymer content (% by weight) φ satisfies the following formula: 40 ≦ φ ≦ 65 (4), and a reaction mixture is continuously taken out from the reaction zone. Production method. 2. The method for producing a methacrylic polymer according to claim 1, wherein the amount of said radical polymerization initiator satisfies the following formulas (1b), (2) and (3b). 10 <(A / B) ^1/2 × 10 ³ (1b) A ≦ 0.5 × 10 ⁻⁴ (2) 0.034 ≦ B ≦ 0.3 (3b) (A and B are as defined above. .)