JPH03212447A - Thermally stabilized polycarbonate resin composition - Google Patents

Abstract

PURPOSE:To obtain a thermally stabilized polycarbonate resin composition increasing thermal stability in a hot molding and giving a molded article with excellent quality by mixing a polycarbonate resin with a specific sulfur-based compound having a large molecular weight. CONSTITUTION:(A) A polycarbonate resin obtained by a reaction of bisphenol-A with diphenyl carbonate in an inert gas, etc., is mixed with (B) 0.05-1wt.% pentaerythritol-tetrakis-sulfur-based compound [e.g. pentaerythritol-tetrakis(beta- laurylthiopropionate)] expressed by the formula (R is 10-20C alkyl; (n) is 1-5) and further an ultraviolet-absorber, coloring agent or lubricant, etc., is added, as necessary, to afford the objective polycarbonate resin composition having extremely increased thermal stability in a hot molding.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to heat stabilized polycarbonate resin compositions.

Conventional technology Polycarbonate resins are generally used in a wide range of fields because they have excellent electrical properties, dimensional stability, self-extinguishing properties, high impact strength, excellent heat resistance, and transparency. has been done.

However, polycarbonate resins generally have a high glass transition point and are molded at high temperatures, so during the molding process, the resin turns yellow due to thermal decomposition or undergoes molecular breakage (zey breakage), causing some of the resin molecules to deteriorate. There was a problem in that the mechanical strength of the molded product was significantly lowered because it was broken into low molecular weight molecules. Such problems became even more serious when polycarbonate resin was molded at a high temperature of 300° C. or higher.

Problems to be Solved by the Invention In order to prevent polycarbonate resin from yellowing during high-temperature molding and from becoming lower in molecular weight due to molecular destruction, conventionally, phenolic antioxidants and phosphorus oxidants have been used as heat stabilizers. Inhibitors and sulfur-based antioxidants such as dialkylthiodipropionates have been incorporated.

However, among these compounds, when phenolic antioxidants are added to polycarbonate resin, they not only have little thermal stabilizing effect, but also cause the hydroxyl groups of phenol to accelerate the decomposition of polycarbonate resin. There was a problem that it had a negative effect and was undesirable.

In addition, the above-mentioned phosphorus-based antioxidant has excellent thermal stability when added to polycarbonate resin, but it is difficult to handle because it easily hydrolyzes in the air, and it is difficult to handle, especially at high temperatures. There is a problem that decomposition occurs, causing discoloration of the polycarbonate resin or generation of bubbles in the resin.

In this case, discoloration refers to when polycarbonate resin, which is originally transparent, becomes colored due to molecular destruction of the resin or self-decomposition of the antioxidant added to it during high-temperature molding. The meaning includes both cases where the color of the transparent polycarbonate resin changes.

Furthermore, conventional sulfur-based antioxidants such as dialkyl thiodipropionates have very little thermal stabilizing effect when added to polycarbonate resins. In order to obtain the same thermal stabilizing effect as the above-mentioned phosphorus-based antioxidant, it is necessary to use a very large amount of the sulfur-based antioxidant. In addition to causing new problems such as discoloration of the resin and bleeding of the sulfur-based antioxidant onto the resin surface, there was also the problem of extremely high costs.

Here, examples of conventional sulfur-based antioxidants such as dialkylthiodipropionate include dilaurylthiodipropionate, distearylthiodipropionate, simiristylthiodipropionate, and laurylstearyl. Thiodipropionate, and distearyl β, β'-thiodibutyrate.

For these reasons, phosphorus-based antioxidants are currently often used as thermal stabilizers for polycarbonate resins, albeit reluctantly.In order to prevent the self-decomposition of phosphorus-based antioxidants at high temperatures, It is necessary to set the upper limit temperature during molding as low as possible and perform strict temperature control to mold the product at low temperatures and in a state of high viscosity. The problem was that it was difficult to obtain.

The purpose of this invention is to solve the problems of the prior art described above by blending a specific sulfur-based compound with a large molecular weight into polycarbonate resin, and to improve thermal stability during high-temperature molding. During molding, it is possible to reduce the residual stress (strain) of the molded product without discoloring due to thermal decomposition or generating bubbles in the resin, and because some of the resin molecules are reduced due to molecular destruction. It is possible to obtain high-quality molded products without molecularization and a decrease in the mechanical strength of the molded product.In addition, the moldable temperature range has become extremely wide, making it possible to avoid the conventional harsh conditions. Temperature control is no longer required, which greatly eases molding conditions, and it is also extremely easy to mold thin-walled products.Moreover, certain sulfur-based compounds can have a large thermal stabilizing effect even when added in small amounts. is obtained, so
There is no bleeding to the resin surface, and the cost is low.
Another object of the present invention is to provide a heat-stable polycarbonate resin composition that is very stable in air and therefore easy to handle and can be manufactured easily and with excellent workability.

Means for Solving the Problems In order to achieve the above-mentioned objects, the present invention provides - maximum: % formula %] (in the formula, R is an alkyl group having 10 to 20 carbon atoms, and n is 1 to 20 carbon atoms).
The gist of the invention is a heat-stabilized polycarbonate resin composition containing a pentaerythritol-tetrakis-sulfur compound represented by the following integer:

The above polycarbonate resin means a polyester of carbonic acid and dihydric phenol expressed in -maximum % formula %, but what is usually called a polycarbonate resin is a polycarbonate ester made from bisphenol.
It is represented by the structural formula of

H3 [OC>-C-1c> -0-Co-] nH
3 As a method for producing such a polycarbonate resin, 2,2-bis(4-oxyphenyl)propane, that is, bisphenol A, and phosgene are mixed with an oxygen binder such as pyridine or caustic alkali, and methylene chloride, chlorobenzene, or xylene. by reacting in the presence of a solvent such as
The so-called solvent method for producing polycarbonate resin and the so-called melt method for producing polycarbonate resin by reacting bisphenol A and diphenyl carbonate in an inert gas are known, and the polycarbonate resin composition according to the present invention All such generally known polycarbonate resins can be used in the product.

Further, the above-mentioned pentaerythritol tetrakis sulfur compound is represented by -maximum: % formula %]. In the formula, R is an alkyl group having 10 to 20 carbon atoms, and n is an integer of 1 to 5.

Here, if the number of carbon atoms in the alkyl group R of the sulfur-based compound is 9 or less, it will easily sublime during molding, contaminating the molded product and the molding machine. Conversely, if the number of carbon atoms in the alkyl group R is 21
If it is more than that, the compatibility with the polycarbonate resin becomes poor and a bleeding phenomenon of the sulfur-based compound occurs, which is not preferable.

Further, if the integer n in the general formula of the sulfur-based compound is 0 or 6 or more, the effect of preventing discoloration and lower molecular weight due to thermal decomposition will not be observed.

Specific examples of pentaerythritol-tetrakis-sulfur compounds include pentaerythritol-tetrakis (
β-laurylthiopropionate), pentaerythritol-tetrakis (stearylthiopropionate),
Examples include pentaerythritol-tetrakis (laurylthiobutyrate), pentaerythritol-tetrakis (myristylthiopropionate), and pentaerythritol-tetrakis (laurylthioacetate).

The amount of the pentaerythritol-tetrakis-sulfur compound is preferably 0.05 to 1.0% by weight based on the weight of the polycarbonate resin.

Here, if the amount of the pentaerythritol-based tetrakis-sulfur compound is less than 0.05% by weight, the effect of preventing discoloration and lower molecular weight due to thermal decomposition will not be observed. Also, if the amount of sulfur-based compounds exceeds 1.0% by weight,
Although these effects are observed, they are not preferable because they cause a bleed phenomenon of sulfur-based compounds.

The heat-stabilized polycarbonate resin composition according to the present invention can be obtained by blending a pentaerythritol-tetrakis-sulfur compound with a polycarbonate resin, and any commonly known blending method may be used for the blending method. .

This method involves heating and mixing polycarbonate resin powder or pellets with a pentaerythritol tetrakis sulfur compound using a mixer, and mixing polycarbonate resin powder or pellets with a sulfur compound using a melt extruder. Examples include a method of melt-mixing and then extruding to pelletize.

Examples of the mixer include a cylindrical mixer, a Nauta mixer, a double cone mixer, a V-type mixer, a Henscheln mixer, a ribbon mixer, and the like.

Note that, of course, ultraviolet absorbers, colorants, lubricants, etc., which are usually added to polycarbonate resins, may also be added to the heat-stabilized polycarbonate resin composition according to the present invention.

Effect According to the polycarbonate resin composition of the present invention, the pentaerythritol fist tetrakis sulfur compound contains 1
What are the four sulfur atoms in the molecule?By adding them to polycarbonate resin, an extremely excellent thermal stabilizing effect can be obtained. A greater heat stabilizing effect can be obtained with a smaller amount added than a heat stabilizer made of a sulfur-based antioxidant such as Nate. In other words, the polycarbonate resin composition containing the pentaerythritol-tetrakis-sulfur compound of the present invention has improved thermal stability during high-temperature molding compared to conventional ones, making it possible to mold at high temperatures and reducing residual stress ( distortion) can be reduced. In addition, the moldable temperature range becomes extremely wide, eliminating the need for strict temperature control as in the past, which not only greatly eases molding conditions, but also makes it extremely easy to mold thin-walled molded products.

Examples Examples 1 to 4 Next, examples of the present invention will be explained together with comparative examples. Examples 1 to 4 Pentaerythritol was added to pre-dried polycarbonate resin powder having a weight average molecular weight of 27,000 (trade name "Nipilon" manufactured by Mitsubishi Gas Chemical Co., Ltd.). -tetrakis (β-
laurylthiopropionate) (sulfur-based compound A) (
(trade name Sumilizer TP-D, manufactured by Sumitomo Chemical Co., Ltd.), 0.05% by weight (Example 1), 0.3% by weight (Example 2), 0.5% by weight (Example 3), and 1 These polycarbonate resin powders and sulfur-based compound A were mixed using a V-type mixer, and then molded at a molding temperature of 3 using an injection molding machine.
Three types of polycarbonate resin plates of the present invention having a thickness of 2 cm were manufactured by molding at 40°C.

Comparative Examples 1 to 12 Next, for comparison, the same polycarbonate resin powder as in Example 1 was used, but polycarbonate resin was prepared in the same manner as in Example 1, except that no heat stabilizer was added. A plate was manufactured (Comparative Example 1).

For comparison, conventional phenolic antioxidants (Comparative Examples 2 and 3.4) and phosphorus antioxidants (Comparative Examples 5 and 6.7) were added to the same polycarbonate resin powder as in Example 1.
) and a sulfur-based antioxidant consisting of dialkylthiodipropionate (Comparative Examples 8 and 9.10) at 0.05% by weight, 0.3% by weight, and 0.5% by weight, respectively.
A polycarbonate resin board was produced in the same manner as in Example 1, except that the ratio of 196% was used.

Here, as the phenolic antioxidant, tetrakis[methylene-'5(3-5-dit-butyl-4'-hydroxyphenyl)propionate (phenolic antioxidant B) (trade name Irganox-1010 , manufactured by Ciba-Geigi Co., Ltd.) was used.

Further, as the phosphorus-based antioxidant, tris(2,4-di-butyl-phenyl) phosphite (phosphorus-based antioxidant C) (trade name: Sumilizer P-16, manufactured by Sumitomo Chemical Co., Ltd.) was used.

As the sulfur-based antioxidant made of dialkylthiodipropionate, distearyl-3゜3''-thiodipropionate (sulfur-based antioxidant D) (trade name: Sumilizer TPS, manufactured by Sumitomo Chemical Co., Ltd.) was used. .

For comparison, 0.02% by weight of the same pentaerythritol-tetrakis (β-laurylthiopropionate) (sulfur-based compound A) as in Example 1 was added to the same polycarbonate resin powder as in Example 1 above. (Comparative Example 11) and 1.5% by weight (Comparative Example 12), except that a polycarbonate resin plate was produced in the same manner as in Example 1.

Comparative Test 1 Next, in order to evaluate the thermal stability of the various polycarbonate resin plate samples obtained in the above Examples and Comparative Examples, the yellowing index (ΔYI) was measured using a color difference meter.

That is, on each side, the polycarbonate resin compound was allowed to stay in the cylinder of the injection molding machine for 10 minutes, and then the yellowness of various sample pieces obtained from the molded polycarbonate resin plate was measured using a color difference meter. The yellowness at that time was defined as Y I ,o. In contrast, the residence time of the polycarbonate resin compound in the cylinder of each injection molding machine was set to 0 minutes, and the yellowness of various sample pieces obtained from each molded polycarbonate 1 resin plate was measured with a color difference meter.
The yellowness at this time is YIo, and these yellowness Y11
The difference between the yellowness index YIo and the yellowness index YIo was defined as the yellowness index of each sample piece, that is, the yellowness index ΔY I '' Y I 1o Y I o , and the obtained results are summarized in Table I.

In addition, we also examined whether foaming occurs in the resin during molding with an injection molding machine, and the obtained results are listed in the "foaming" column in Table I. The samples where foaming did not occur were marked as ○, and the samples where foaming occurred and the yellowness could not be measured were marked with a symbol.

In addition, in the same way, the polycarbonate resin plate after molding is
We also tested whether or not a lead occurs, and the obtained results are shown in the "Bleed" column in the same table, with those in which no bleed occurred as Q1 and those in which bleed occurred, and
Described with symbols.

As can be seen from the results in Table I, the molded plate of the polycarbonate resin composition obtained in the example of the present invention has a very small value of yellowing degree ΔYl, and therefore has improved thermal stability during high temperature molding. Even when molded under high temperature conditions of 340℃, there is very little discoloration due to thermal decomposition, no air bubbles are generated in the polycarbonate resin, and there is no bleeding in the polycarbonate resin plate after molding. , it is clear that it has very good quality.

On the other hand, the conventional polycarbonate resin molded plates obtained in each comparative example had very large values of yellowing degree ΔY■, and therefore had poor thermal stability during high-temperature molding, and discoloration due to thermal decomposition. It was happening.

In particular, in Comparative Examples 3, 4, and 6.7, in which conventional phenolic antioxidants and phosphorus antioxidants were used, air bubbles were generated in the polycarbonate resin. In Comparative Example 9゜10, which was added to the polycarbonate resin, and Comparative Example 12, in which the amount of pentaerythritol tetrakis sulfur compound A was increased, bleeding occurred in the polycarbonate resin plate after molding, and eventually were also of inferior quality.

Comparative Test 2 In order to evaluate the thermal stability of the polycarbonate resin molded plate, the polycarbonate resin formulation in Example 2 and various polycarbonate resin formulations in Comparative Example 3, Comparative Example 6, and Comparative Example 9 were tested in After mixing using a mold mixer, the mixture was molded using an injection molding machine at molding temperatures of 280°C and 340°C to produce various polycarbonate resin plates.

For the various polycarbonate resin plate samples obtained in this way, optical distortion (birefringence rv
) were measured, and the obtained results are summarized in Table H.

Note that the smaller the birefringence index, the less distortion there is.

Also, in Table 1, the results of testing whether foaming occurs in the resin during molding using an injection molding machine at 340° C. are added, as in Table I.

As can be seen from the results in Table 2, Example 2 of this invention
The molded plate of the polycarbonate resin composition obtained in the above has a very small birefringence value at both molding temperatures of 280°C and 340°C, and therefore has improved thermal stability during high-temperature molding. It is clear that the polycarbonate resin molded plate has little distortion and has very excellent quality.

On the other hand, the conventional polycarbonate resin molded plates obtained in Comparative Examples 3 and 6 had a very large birefringence value when the molding temperature was 280°C, and the distortion of the polycarbonate resin molded plates was large. Therefore, the thermal stability during high temperature molding was poor. In addition, in these comparative examples, when the molding temperature was 340° C., it was impossible to measure the birefringence index because bubbles were generated in the resin.

In addition, the conventional polycarbonate resin molded plate obtained in Comparative Example 9 has a small birefringence value when the molding temperature is 280°C, and the distortion of the polycarbonate resin molded plate is small, but when the molding temperature is 340°C. In the case of , the value of birefringence is much larger than that of Example 2 of the present invention, and the distortion of the polycarbonate resin molded plate is large.
Therefore, it can be said that the thermal stability during high temperature molding is poor.

Effects of the Invention As mentioned above, the heat-stabilized polycarbonate resin composition according to the present invention has -maximum: % formula % (wherein R is an alkyl group having 10 to 20 carbon atoms, and n is 1 to
(an integer of 5), and by blending a specific sulfur-based compound with a large molecular weight into the polycarbonate resin, the thermal stability during high-temperature molding can be improved. , during high-temperature molding, there is no discoloration due to thermal decomposition or generation of bubbles in the resin, and the residual stress (strain) of the molded product can be reduced. It is possible to obtain high-quality molded products without reducing the mechanical strength of the molded products due to low-molecular-weight molecules, and the temperature range at which molding can be performed has become extremely wide. Strict temperature control is no longer necessary, which greatly eases molding conditions. It is also extremely easy to mold thin-walled products, and certain sulfur-based compounds can provide significant thermal stabilization even when added in small amounts. It is effective, does not bleed onto the resin surface, is inexpensive, and is extremely stable in the air, making it easy to handle and easy to manufacture.
This effect is achieved.

that's all

Claims (2)

[Claims] (1) General formula: [RS-(CH_2)_n-COOCH_2]_4C(
In the formula, R is an alkyl group having 10 to 20 carbon atoms, and n is 1 to 5
A heat-stabilized polycarbonate resin composition containing a sulfur-based compound represented by (an integer of ). (2) The amount of the sulfur-based compound added is 0.05 to 1.0
The heat stabilized polycarbonate resin composition according to claim 1, which is % by weight.