JPS61278511A - Partial metal salt of styrene/methacrylic acid copolymer resin - Google Patents

Abstract

PURPOSE:To obtain a thermoplastic resin which is odorless and excellent in heat resistance, by using a styrene/methacrylic acid-methacrylic acid metal salt tercopolymer having a specified residual methacrylic acid monomer content and a specified residual styrene monomer content as a component. CONSTITUTION:In the production of a styrene/methacrylic acid/methacrylic acid metal salt tercopolymer comprising 99-45mol% styrene units, 0.9-54.9mol% methacrylic acid units and 0.1-54.1mol% methacrylic acid metal salt units, wherein the content of residual methacrylic acid monomer is 0.01pt.wt. or below per 100pts.wt. copolymer and the content of residual styrene monomer content is 0.2pt.wt. or below, a mixture of styrene with methacrylic acid is solution-polymerized and the reaction product is subjected to vacuum treatment at 220-250 deg.C and 1-100Torr in the 1st devolatilizer. This copolymer is led to a kneader, where it is kneaded well with an injected aqueous metal salt solution to convert the methacrylic acid units of the tercopolymer into a partial metal salt. This product is sent through a preheater to the 2nd devolatilizer, where it is subjected again to vacuum treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a thermoplastic resin that has excellent heat resistance and is odorless.

In recent years, there has been an extremely strong demand for resins that have excellent heat resistance, are odorless, and are inexpensive for microwave food containers.

[Conventional technology]

Among the resins currently on the market, polycarbonate is well known as a resin with excellent mechanical strength and heat resistance, but because this resin is expensive, it is not used for food containers in microwave ovens, etc. do not have.

On the other hand, polystyrene is a colorless and transparent resin that is commercially available at the lowest price, but its uses are limited because of its poor heat resistance.

Therefore, as a method to further improve heat resistance while maintaining the characteristics of polystyrene, which is inexpensive and has good processability,
A well-known method is to copolymerize styrene with methacrylic acid. A continuous process is the most common method for manufacturing this styrene and methacrylic acid copolymer (hereinafter abbreviated as SMAA resin), and the details are described in U.S. Patent No. 3.03.
The disclosure is in the specification of No. 5033. On the other hand, a method for producing SMAA resin using a suspension polymerization method is also known (Japanese Unexamined Patent Application Publication No. 2003-120002). As described above, there are various disclosures regarding this SMAA resin, and more recently, it has been industrially produced. However, this SMAA resin has two drawbacks, making it difficult to use it for food containers in microwave ovens.

One of the problems is odor. At high temperatures, SMAA resin
For example, when used as tableware at /θo-1ro°C, unlike polystyrene, the degree of thermal deformation is small, but it emits a characteristic odor, which significantly reduces its value. Another problem is oil resistance.

In the case of polystyrene, when it comes into contact with food oil while being heated in a microwave oven, etc., the container first deforms and is often attacked by the oil pressure of the food at the same time. Unlike polystyrene, SMAA resin has a much smaller degree of deformation and exhibits some oil resistance when in contact with food oil, but it is not perfect. Despite its problems, the use of SMAA resin is still subject to significant limitations.

[Problem that the invention seeks to solve]

Therefore, the inventors of the present invention have conducted intensive research to solve the problem of odor, and have found that if this resin is sufficiently purified, the copolymer itself is completely odorless, and the accompanying components are odorless. It was discovered that this caused a problem. As a result of further detailed study on this point, the inventors found that 8M
It has been found that when the content of methacrylic acid monomer and styrene monomer as monomer components remaining in the AA resin exceeds a certain amount, it acts to strengthen the odor of the resin.

Next, as a result of repeated research into the problems of heat resistance and oil resistance, one solution was to simply increase the methacrylic acid units that make up the copolymer, but the effect was not sufficient. Furthermore, it has been found that it is more effective to use a third component as a copolymer constituent. Acrylonitrile can be considered as this third monomer component, but in this case acrylonitrile is not preferred because it easily reacts with methacrylic acid and becomes a gel state.

Methyl methacrylate is another third component, but its effect is not that great. Therefore, the present inventors improved heat resistance and oil resistance by modifying a part of the methacrylic acid unit into a methacrylic acid metal salt, rather than introducing other monomers as a third component. Mourning to find that they are satisfied at the same time.

The purpose of the present invention is to further improve the heat resistance and oil resistance by reducing each monomer component in the SMAA resin and at the same time modifying the SMAA resin. Our goal is to provide resin at low prices.

[Means for solving problems]

That is, the present invention provides the styrene units 97 to Il! Styrene-methacrylic acid-metal methacrylate ternary copolymer 1 consisting of mol%, methacrylic acid unit O1 ~ jIA tamol.%, methacrylic acid metal salt O1 / ~ jIA1 mol%
0θ parts by weight. (Bl methacrylic acid monomer is 0.0 parts by weight or less). (0) The present invention provides an odorless thermoplastic heat-resistant resin characterized in that the content of styrene monomer is v2 parts by weight or less.

The greatest feature of the present invention is that when a styrene-methacrylic acid binary copolymer is transformed into a styrene-methacrylic acid-methacrylic acid metal salt terpolymer by a unique chemical modification method, the ternary copolymer is simultaneously This significantly reduces the content of residual monomers in the polymer. There have already been many reports on ionic polymers [for example,
L,Ho1liday, Ionic Polymers
), Applied 5cienee Publish
ers LTD, +London+ (/ri7j)], there has never been a description of a product with significantly reduced residue as in the present invention.

Regarding the resin of the present invention, first, the binary copolymer immediately after polymerization is composed of random bonds of styrene units and methacrylic acid units, and then the methacrylic acid units are partially converted into methacrylic acid metal salts. Both the acid and its metal salt units play a role in improving heat resistance, and their total amount ranges from / to jj molti based on the copolymer. Furthermore, within this range the methacrylic acid units are Ol. 9 to 54.9 mol%, methacrylic acid metal salt unit is 0. /-! 'It is essential that it be within the range of A1 molti. If the total amount is less than 1 molt, it is impossible to improve heat resistance. If it exceeds the molten limit, the melt fluidity of the resin decreases, leading to a decrease in processability, which is not preferable. Conversely, the styrene unit is ≠ due to its moldability! It is essential that the amount is between 10% and 99%. Next, 1 this methacrylic acid and its metal salt/~j
The metal methacrylate salt is required to be at least 0.1 mole in the j mole, and if it is less than 0.1 mole, no further improvement in heat resistance or oil resistance can be expected. Therefore, the required amount of methacrylic acid and its metal salts is determined.

Next, the metal forming the methacrylic acid metal salt is preferably selected from metals having a valence of 7 to 3 from Groups I, 11, I, M-A, and ■ of the periodic table. is Na,
K% C11% fi, zn, BaxCo) Nix and AI. Especially among these, Na, Mg,
Zn is effective, and Na and K are more preferred.

In the resin of the present invention, when the styrene-methacrylic acid-methacrylic acid metal salt copolymer is 10[theta] parts by weight, the content of the methacrylic acid monomer must be 0.0j weight or less, more preferably 0.0j parts by weight or less. 0.07 parts by weight or less. Originally, it is desirable for the entire amount of methacrylic acid monomer to be polymerized and converted during the polymerization process, but no matter which radical polymerization method is used, such as bulk polymerization, solution polymerization, suspension polymerization, or a combination thereof, it is not possible to completely convert the methacrylic acid monomer into a polymer. It remains as an unreacted component without being converted into. This residual monomer can be separated and removed by treating the polymer in a molten state under reduced pressure, but since the vapor pressure of the methacrylic acid monomer is relatively low, removal is not easy. Next, a step of converting some of the methacrylic acid units of this SMAA resin into methacrylic acid metal salt units is carried out to finally obtain the desired resin, but there is no methacrylic acid monomer in this resin. If the amount exceeds .01 part by weight, when the resin is used at high temperatures after being molded into food containers, it will emit an unpleasant odor characteristic of methacrylic acid, giving an unpleasant feeling. Furthermore, in this case, if the methacrylic acid monomer exceeds 0.07 parts by weight when molding by injection molding or the like, the screw or mold of the injection molding machine may be corroded. Styrene, another monomer component, similarly emits an unpleasant odor depending on its residual amount, but in this case, it is less than 12 parts by weight of O, more preferably 0.1
It is necessary that the amount is not more than parts by weight. If it exceeds 0.2 part by weight, the odor will cause discomfort.

Since the resin of the present invention is processed into injection molded articles, extruded sheets, or foamed articles, it must have an appropriate melt viscosity. The melt flow rate (MFR) when the measurement conditions are 230° C. and a load of 3JKti is preferably between 017 and 209710 minutes. When VFR is less than 07, processability tends to decrease, molecular weight and/or metal chloride degree decreases, and when MFR exceeds 20, mechanical strength tends to decrease.

To produce SMAA resin, which is a precursor of the resin of the present invention,
All conventional free-radical polymerization methods may be used, but continuous bulk or continuous solution or suspension polymerization methods are particularly preferred. In either case, a devolatilization process is required to effectively remove residual unreacted monomers, and further improvements are required to this process.

For example, in the case of a continuous solution polymerization method, it is preferable that the polymerization reactor be a complete mixing type, in which monomers of styrene and methacrylic acid, aromatic hydrocarbons such as) luene and ethylbenzene, acetone, methyl ethyl ketone, methyl isobutyl ketone, etc. Ketones etc. as a solvent! ~10% by weight is used. The polymerization is carried out at a temperature ranging from 10 DEG C. to /JO DEG C., and the polymerization conversion of the monomers is 20-11% by weight. The polymer solution leaving the polymerization process after being heated in this manner is heated to 220℃~220℃.
It is continuously fed to the first stage devolatilizer which is heated by JO'cK and the pressure is reduced to 1w100 Torr, and most of the unreacted monomers and solvent are removed. The polymer discharged from the seventh stage devolatilizer is SMAA resin, and is partially converted into metal salts by the following two methods. First, the first method is to send the molten resin from the seventh stage devolatilizer to the second stage devolatilizer via piping. An effective kneader is installed in a part of the piping after this first-stage devolatilizer, and this kneader is filled with formate, acetate, and the like of the target metal to modify the methacrylic acid units in the resin. Oxides, hydroxides, methoxides, ethoxides, carbonates, and bicarbonates are injected as aqueous solutions, thoroughly kneaded, and passed through a necessary preheater before being sent to the second stage devolatilizer and heated to 210'C again. ~2!0℃. 1-54.1O
Perform OTorr high temperature decompression treatment. In the second method, the molten resin discharged from the first stage devolatilizer in the continuous polymerization process is cooled, solidified, and shredded into granules.

This resin is SMAA resin, and is subjected to metal chlorination treatment using an extruder combined with the following two stages. First, granular SMAA resin is fed into the seventh stage extruder, and at the tip of this extruder, a formate, acetate, oxide, or hydroxide of the target metal is added to the tip of the extruder. , methoxide, ethoxide, carbonate, bicarbonate as an aqueous solution and kneading.

The mixture discharged from the first stage extruder is melt-fed to the first stage extruder, and is devolatilized by reducing the pressure of the single or plural vent holes of the second stage extruder to /N100 TorrVC.

No matter which of these two methods is used, the desired amount of methacrylic acid units in the resin can be very effectively converted into metal methacrylate with the desired metal, and at the same time, the second step can be carried out. The residual monomer is extremely effectively reduced during the devolatilization water flushing process.

In addition to such a continuous solution method, SMAA resin can be obtained by a known suspension polymerization method, but in this case as well, the bead-shaped polymer after polymerization is processed using the two-stage extruder device mentioned above. Similarly, metal chlorination and devolatilization can be effected effectively using K.

The resin obtained in this way can be processed into injection molding, extrusion sheets, or biaxially oriented sheets as is, but if necessary, heat stabilizers, light stabilizers, nonionic surfactants, anionic interfaces, etc. As an activator and lubricant, liquid paraffin, higher fatty acids with a carbon number of g-22, metal #i (calcium, i-gnesium, zinc) of higher fatty acids with a carbon number of g to 22, ethylene bis fatty acid (C16, C1g) amide, high grade fatty acids are used as activators and lubricants. Aliphatic alcohols, adipic acid, dibutyl or dioctyl esters of sebacic acid, mono-, di-, and triglycerides of higher fatty acids having t to 2 carbon atoms, hydrogenated castor oil, dimethylpolysiloxane, and the like are added.

〔Effect of the invention〕

The thermoplastic resin of the present invention does not deform even at high temperatures of 100°C or higher, is odorless and has a pleasant appearance, and can be processed into highly safe molded products such as microwave food containers. It is excellent.

〔Example〕

EXAMPLES Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way.

In addition, the measurement method of each physical property is as follows.

(1) Picat softening temperature: ASTM-D yr2r (
2) Determination of odor: After heating the injection molded piece to 700° C. in a closed container, the odor was determined.

(8) Compositional analysis of polymer /-j polymer 1i[ace(metac 1)/'' acid unit ton, methyl ethyl ket
Titrate the DMF solution with 7N alcoholic NaOH (t or KOII) using phenolphthalene as an indicator.

(4) Method for measuring monomers in resin Using gas chromatography (Takashi Seisakusho ICM),
Measured by internal standard method. The conditions are as follows.

(a) Styrene monomer measurement conditions Hydrogen flame detection method Column packing material: PEG-400010%, J@
Column temperature: l≠O℃ Inlet temperature = 2. ! 0°C Carrier gas: N2 Hj 047 minutes The sample is a 5% by weight dimethylformamide solution.

(b) Methacrylic acid monomer measurement conditions Hydrogen flame detection method Column packing material: PEG-4000, 20%, j
m column temperature: l≠! ℃ Inlet temperature: 2tao℃ Carrier gas 2N2. The ♂0m17 minute sample is a 5% by weight methyl ethyl ketone solution.

(6) Oil resistance and heat resistance A biaxially stretched sheet is immersed in salad oil heated to 700°C, and its appearance is evaluated.

The following resins were prepared as well-known resins for comparison with the copolymer resin of the present invention.

polystyrene , weight average molecular weight Nico♂roo.

MF'RC, 230°C, 3. ♂Kf): Ta, Hiroshi 9
/10 minutes Example/ Continuous solution polymerization was carried out using an apparatus made entirely of stainless steel. Styrene/7yoλ weight%, methacrylic acid IAr]t'Ik%, and ethylbenzene-0 weight% were used as a preparation solution, and as a polymerization initiator, 41-di-tart-butylperoxy-J,! ,! -trimethylcyclohexa/
l-used. This blended solution f was continuously fed at a rate of /73/hr to a complete mixing polymerization vessel with an internal volume of 1 and equipped with a stirrer, and polymerization was carried out at /36°C. Solid weight%
Continuously take out the polymerization solution containing 2JOT:
, After K preheating, keep warm at 23 o'cIlc, and then OTo in the evening.
rr K is supplied to the first stage devolatilizer under reduced pressure, and the average retention WI
After O,j hours have passed, it is discharged to the piping from the bottom gear pump of the devolatilizer. A caustic soda aqueous solution is injected into an efficient mixer installed in this pipe, and after mixing with the molten resin,
The first stage devolatilizer is introduced via the preheater. 230℃,
' After staying for an average of 0.2 hours under reduced pressure of Torr,
Take out the resin. The properties of this resin are shown in Table 1.

Comparative Example 1 In Example 1, the resin discharged from the first stage devolatilizer was directly cooled and made into granules. The properties of this resin are
Write it down in the table.

Example λ The resin obtained in Comparative Example/ is processed using two extruders connected together. First, the granular resin obtained in Comparative Example/Ao Oni's twin-screw presser K was fed at a rate of 2 kg/)Ir. Next, the caustic potassium aqueous solution that had been pumped separately from the only vent hole of this twin-screw extruder was injected, and after being sufficiently kneaded at the tip of the extruder, it was passed through a 230" CK heat-insulated piping. It is fed in a molten state to a two-stage CoOX single-screw extruder.

This single screw extruder is! Depressurization degree of ventro at O℃/jT
It is orr. The resin thus obtained is shredded into particles. The properties of this resin are shown in the liX/table.

Example 3 In Example 1, the polymerization mixture was 77.2% by weight of styrene and methacrylate! Polymerization, devolatilization, and modification treatments were carried out in exactly the same manner except that the weight ratio was 20% by weight of ethylbenzene. The properties of this resin are shown in Table 1.

Comparative Example 2 In Example 3, the resin discharged from the first stage devolatilizer was directly cooled and made into granules. The properties of this resin are
Write it down in the table.

Example The following components were supplied to a stainless steel autoclave.

Styrene l≠A! 9 methacrylic acid, 225 dihydrate
Otsu 7Kf Hydroxy Cellulose /,! 9 lauryl mercaptan
Ta09 Azoshiinobutyronitrile
A mixed solution of 1Aj9 etc. was stirred vigorously and heated to 77° C. under a nitrogen atmosphere. After 3 hours, reduce the temperature and
1. Stir for 5 hours to complete the reaction. Ta. The product was then cooled, centrifuged, washed with water and dried at 70°C. The resulting bead-shaped resin was transparent and colorless, and as a result of compositional analysis by neutralization titration of this resin, the methacrylic acid unit was /3
．． /Yogmorchi (/Yogumorchi), styrene unit is g6. % by weight (r1 mole). This beaded resin was then prepared in the same apparatus and in the same manner as in Example 2, but with KO
The operation was carried out by injecting a NaOH aqueous solution instead of the aqueous solution. The properties of the obtained resin are shown in Table 2.

Comparative Example 3 A bead-shaped resin obtained by suspension polymerization in the same manner as in Example μ was subjected to devolatilization treatment using a single-screw extruder equipped with a vent.
No metal salt aqueous solution was added. The properties of the obtained resin are shown in table fIIJ2.

Comparative Example ≠ A bead-shaped resin obtained by suspension polymerization in the same manner as in Example D was treated in the same apparatus and in the same manner as in Example D, but with the exception of KOI.
(The operation was carried out by injecting water instead of the aqueous solution. The properties of the obtained resin are shown in Table 2.

(Margin below) Table 2

Claims (3)

[Claims] (1) (A) Styrene-methacrylic acid-methacrylic acid consisting of 99 to 45 mol% of styrene units, 0.9 to 54.9 mol% of methacrylic acid units, and 0.1 to 54.1 mol% of methacrylic acid metal salt units. A metal salt terpolymer containing (B) 0.01 parts by weight or less of residual methacrylic acid monomer and 0.2 parts by weight of (C) residual styrene monomer based on 100 parts by weight of the copolymer. An odorless thermoplastic heat-resistant resin characterized by having an odorless content of less than (2) (A) Styrene-methacrylic acid-methacrylic acid consisting of 99 to 45 mol% of styrene units, 0.9 to 54.9 mol% of methacrylic acid units, and 0.1 to 54.1 mol% of methacrylic acid metal salt units. A metal salt terpolymer containing (B) 0.01 parts by weight or less of residual methacrylic acid monomer and 0.2 parts by weight of (C) residual styrene monomer based on 100 parts by weight of the copolymer. In the production of an odorless thermoplastic heat-resistant resin having a temperature of less than 220℃~250℃, 1~100
The resulting molten copolymer is treated under reduced pressure with Torr, and then introduced into a kneader where an organic or inorganic metal salt aqueous solution is injected and sufficiently kneaded to partially metallize the methacrylic acid units of the binary copolymer. A manufacturing method characterized in that the product is then sent to a second stage devolatilizer via a preheater and subjected to the above-mentioned depressurization treatment again. (3) (A) Styrene-methacrylic acid-methacrylic acid consisting of 99 to 45 mol% of styrene units, 0.9 to 54.9 mol% of methacrylic acid units, and 0.1 to 54.1 mol% of methacrylic acid metal salt units. The metal salt terpolymer contains (B) 0.01 parts by weight or less of methacrylic acid monomer and (C) 0.01 parts by weight or less of residual styrene monomer, based on 100 parts by weight of the copolymer.
In the production of an odorless thermoplastic heat-resistant resin containing 2 parts by weight or less, a binary copolymer is produced by solution polymerization or suspension polymerization of a mixture of styrene and methacrylic acid, and then granular solids of the copolymer are produced. This is introduced into an extruder, and then an aqueous metal salt solution is injected and mixed, and then the pressure is reduced from the vent port of the same extruder to devolatilize it, or after it is introduced into another extruder, it is removed from that extruder. A manufacturing method characterized by devolatilizing by reducing pressure from a vent port.