JP3478345B2 - Thermoplastic resin composition and method for suppressing environmental whitening of thermoplastic resin - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a thermoplastic resin composition,
And a method for suppressing environmental whitening of a thermoplastic resin, more specifically, a thermoplastic resin composition in which environmental whitening is unlikely to occur,
And a method for suppressing environmental whitening of a thermoplastic resin for preparing such a thermoplastic resin composition.

[0002]

2. Description of the Related Art Thermoplastic transparent resins such as polycarbonate are widely used. However, when the thermoplastic transparent resin molded product is held in an environment of high temperature and high humidity such as steam sterilization and returned to room temperature, it may become cloudy and lose transparency.

Regarding polycarbonate as a cause of environmental whitening, many minute disk-shaped cracks are generated in the resin,
It is known that this is because light is diffusely reflected (M. Narkis et al., Journal).
of Applied Polymer Science
e, vol. 27, 2809-2914 (198)
2) and M.I. Narkis et al. , Polym
er Engineering And And Science
e, February, vol. 24, No.
3, 221-217 (1984) etc.). This is because when a resin molded product in which moisture penetrates at high temperature is returned to room temperature, it becomes supersaturated inside the resin and agglomerates, resulting in strain depending on the size of the agglomerated nuclei formed, and when the strain exceeds a certain size. It is thought that this is because a disk-shaped crack is generated. In addition, a disk-shaped crack does not occur near the surface and in the deep part, but it is considered that this is because water easily diffuses out of the resin near the surface and almost no water penetrates in the deep part, so that it is less likely to be oversaturated. .

A method of suppressing the disc-shaped crack which is considered to occur in this way has not been known.

[0005]

DISCLOSURE OF THE INVENTION As a result of earnest research, the present inventors have found that for thermoplastic resins, environmental whitening can be suppressed by dispersing a rubbery polymer in the form of minute microdomains. It came to completion.

[0006]

Thus, according to the present invention, the rubber-like polymer is dispersed in the thermoplastic resin excluding the thermoplastic norbornene-based resin to form microdomains having a particle diameter of 0.5 μm or less. Thermoplastic resin composition and method for suppressing environmental whitening of a thermoplastic resin, wherein the rubbery polymer is dispersed in a thermoplastic resin excluding a thermoplastic saturated norbornene-based resin so as to form microdomains having a particle size of 0.5 μm or less Will be provided.

(Thermoplastic Resin) The thermoplastic resin which is the main component of the thermoplastic resin composition of the present invention is not particularly limited as long as it is a resin that causes environmental whitening, but transparency may be lost due to environmental whitening. It is more preferable that the thermoplastic transparent resin has a haze value of 5 or less when molded into a plate having a thickness of 3.0 mm, and particularly preferably 4 or less. In particular,
Examples include polycarbonate, polystyrene, polyethylene, polyester, polypropylene, poly-4-methylpentene-1 and the like.

[0008] be of thermoplastic resin incompatible used the rubbery polymer (rubbery polymer) present invention, the particle size 0.5μm in thermoplastic resin
Or less, preferably 0.3 μm or less, particularly preferably 0.
There is no particular limitation as long as it can form and disperse 2 μm microdomains. When supersaturated water agglomerates in the resin composition, it tends to agglomerate at the interface. Therefore, it is preferable that the total area of the interface in the resin composition is large, that is, the particle size be small. By reducing the particle size, the resin composition can be made transparent and the magnitude of strain per unit area of the interface can be reduced, as described later. Rubber polymer, Ru buffering action there against distortion caused by the agglomeration of the water vapor.

The rubber-like polymer is preferably a rubber-like polymer which is unlikely to cause elution and the like, and is preferably a rubber-like polymer having a buffering action and a glass transition temperature of 40 ° C. or lower. The block copolymer rubbery polymer or the like may have a glass transition temperature of 2 or more. In that case, if the lowest glass transition temperature is 40 ° C. or lower, the glass transition temperature of the present invention is 40 ° C. It can be used as the following rubbery polymer.

Examples of the rubbery polymer used in the present invention include emulsion-polymerized or solution-polymerized styrene-butadiene-rubber, high-styrene rubber and other random or block styrene-butadiene-based copolymers, and hydrogenation thereof. Isoprene rubber, hydrogenated product thereof; Chloroprene rubber, hydrogenated product thereof; Saturated polyolefin rubber such as ethylene / propylene copolymer, ethylene / α-olefin copolymer, propylene / α-olefin copolymer; ethylene・ Propylene / diene copolymer, α
-Diene-based polymers such as olefin / diene copolymers, diene copolymers, isobutylene / isoprene copolymers, isobutylene / diene copolymers, halides thereof, diene-based polymers or hydrogenated products thereof. Acrylonitrile / butadiene copolymer, hydrogenated product thereof; vinylidene fluoride / trifluoroethylene copolymer, vinylidene fluoride / hexafluoropropylene copolymer, vinylidene fluoride / hexafluoropropylene / tetrafluoroethylene Fluorine rubber such as copolymer, propylene / tetrafluoroethylene copolymer; urethane rubber, silicone rubber, polyether rubber, acrylic rubber, chlorosulfonated polyethylene rubber, epichlorohydrin rubber, propylene oxide rubber, ethylene acrylic rubber, etc. Special rubber; Norbornene-based single Polymer and ethylene or α-
Copolymers of olefins, terpolymers of norbornene-based monomers and ethylene and α-olefins, ring-opened polymers of norbornene-based monomers, ring-opened polymers of norbornene-based monomers, hydrogenated products, etc. Norbornene-based rubbery polymers; random copolymers of styrene / butadiene / styrene / rubber, styrene / isoprene / styrene / rubber, styrene / ethylene / butadiene / styrene / rubber aromatic vinyl-based monomers / conjugated dienes, etc. Hydrogenated products;
Linear or radial block copolymer of styrene / butadiene / styrene / rubber, styrene / isoprene / styrene / rubber, styrene / ethylene / butadiene / styrene / rubber aromatic vinyl monomer / conjugated diene
In addition to styrene-based thermoplastic elastomers such as hydrogenated products thereof, urethane-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, 1,2-polybutadiene-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, fluorine-based thermoplastic elastomers, etc. And the like, and those which are incompatible with the thermoplastic resin as the main component.

Among these, a copolymer of an aromatic vinyl-based monomer and a conjugated diene-based monomer and a hydrogenated product thereof are dispersed in the thermoplastic resin as long as they are incompatible with the thermoplastic resin as the main component. It is usually preferable that it has good properties. The copolymer of the aromatic vinyl-based monomer and the conjugated diene-based monomer may be a block copolymer or a random copolymer. From the viewpoint of weather resistance, it is more preferable that the portion other than the aromatic ring is hydrogenated. Specifically, styrene / butadiene block copolymers, styrene / butadiene / styrene / block copolymers, styrene / isoprene / block copolymers, styrene / isoprene / styrene / block copolymers, and hydrogenated products thereof. , Styrene / butadiene / random copolymer and the like. However, even a combination of a thermoplastic resin and a preferred rubbery polymer may not be incompatible and may not be able to form microdomains, such as a combination of polystyrene and styrene / butadiene / styrene / block copolymer. Yes, such combinations cannot be used to prepare the resin compositions of the present invention.

Further, when the resin composition of the present invention is required to have transparency, it is preferable that the difference in refractive index between the rubber-like polymer and the thermoplastic resin is small. The difference in refractive index is preferably 0.2 or less, more preferably 0.1 or less, and particularly preferably 0.05 or less. In particular, when transparency is required, it is generally 0.02 or less, preferably 0.015 or less,
More preferably, the difference in refractive index is 0.01 or less. When a mixture having a large difference in refractive index is mixed, it becomes opaque when added in a large amount. Although different types of thermoplastic resins have different refractive indices, for example, in rubbery polymers, by changing the ratio of monomers or changing the number of unsaturated bonds in the main chain by hydrogenation, etc. It is possible to change the refractive index. It is preferable to select a rubbery polymer having an appropriate refractive index depending on the refractive index of the thermoplastic resin used.

(Compounding) In the present invention, the rubbery polymer is added to the thermoplastic resin in an appropriate amount to form microdomains in the thermoplastic resin,
Disperse. The addition amount is determined by the combination of the thermoplastic resin and the rubbery polymer, but generally, if the addition amount is too large, the glass transition temperature of the resin composition is significantly lowered, and microdomains are not formed or aggregate. Do not disperse. If the amount of addition is too small, the distance between the microdomains is too large, so that water cannot be aggregated at the interface of the microdomains, but it is aggregated at other portions, which may cause a disk-shaped crack. Rubbery polymerization
Body, with respect to 100 parts by weight of the thermoplastic resin, usually 0.0
1 to 15 parts by weight, preferably 0.02 to 10 parts by weight, more preferably 0.05 to 5, and particularly preferably 0.1 to 2 parts by weight.
Add in parts by weight.

The addition method is not particularly limited as long as the rubbery polymer forms microdomains in the thermoplastic resin and is sufficiently dispersed. For example, a method in which a rubbery polymer is added and kneaded in a state where the resin is melted with a mixer or a twin-screw kneader, or after the rubbery polymer is dispersed by dissolving in a suitable solvent, There is a method of removing the solvent by a coagulation method, a casting method, or a direct drying method.

In the case of kneading, generally, assuming that the glass transition temperature of the resin is Tg, Tg + 20 ° C. to Tg + 150.
At the resin temperature of ℃, apply enough share. If the resin temperature is too low, the viscosity will be high, and it will be difficult to knead. If it is too high, the resin and the rubbery polymer will be deteriorated, and the two cannot be kneaded well due to the difference in viscosity and melting point.

For example, Labo Plastomill (made by Toyo Seiki)
When using, the number of rotations is 20
When kneading at a feed rate of about 70 rpm and a residence time of about 1 to 20 minutes, a rubbery polymer is usually dispersed in a thermoplastic resin to form microdomains having a diameter of 0.5 μm or less. Can be made. Usually, in a twin-screw kneader, L / D is 25 or more, preferably 30
As described above, the residence time is set to about 1 to 20 minutes. The longer the residence time, the easier it is to form microdomains, but the resin and rubbery polymer are likely to deteriorate, so the resin used, the rubbery polymer, and the combination of the devices used for kneading are preliminarily kneaded. It is necessary to decide the number of rotations and the residence time that match the combination.

The microdomains have a substantially spherical shape, and the variation in particle size among particles is small. Usually, the diameter is 0.5 μm or less, preferably 0.3 μm or less, and particularly preferably 0.2 μm or less. When the particle diameter is 0.3 μm or less, the decrease in transparency of the thermoplastic resin composition due to the addition of the rubbery polymer is small as will be described later, and there is no problem .
Even if the microdomains are not spherical, the diameter of the smallest sphere that can confine the microdomains is 0.5 μm or less, preferably 0.3 μm or less,
It is particularly preferably 0.2 μm or less.

(Additives) If desired, various additives may be added to the thermoplastic resin composition of the present invention. Additives used in the resin are compatible with the resin, and include phenol-based and phosphorus-based antioxidants, antistatic agents, ultraviolet absorbers and the like.
When the sheet is formed by the solution casting method, it is also preferable to add a leveling agent in order to reduce the surface roughness.

(Thermoplastic Resin Composition) In the thermoplastic resin composition of the present invention, the rubber-like polymer is usually contained in the matrix of the thermoplastic resin, and the diameter thereof is 0.5 μm or less.
Preferably 0.3 μm or less, particularly preferably 0.2 μm
The following microdomains are formed and dispersed. The wavelength of monochromatic light used for information processing such as information disks and infrared sensors is about 300 nm to 1000 nm, and visible light visible to humans is about 400 nm to 800 nm. The diameter of the rubbery polymer is smaller than the wavelength of these lights,
Light is less likely to be scattered if microdomains of 0.3 μm or less, particularly 0.2 μm or less are formed, so that the thermoplastic resin composition is excellent in transparency.

Further, the thermoplastic resin composition of the present invention, since a small amount of rubber polymer, except that hardly causes environmental whitening, heat resistance, chemical resistance, dielectric properties, rigidity rubber It is substantially the same as the thermoplastic resin to which the quality polymer is not added.

The method for molding the resin composition is not particularly limited. Depending on the purpose, an injection molding method, a blow molding method, an injection blow molding method, a rotational molding method, a vacuum molding method, an extrusion molding method, a calender molding method, a solution casting method and the like are possible.

The use of the resin composition of the present invention is also not limited. In particular, in a transparent resin molded product that is repeatedly used in a high temperature and high humidity environment and at room temperature and room temperature, for example, a medical instrument that is used after steam sterilization, environmental whitening is unlikely to occur, which is preferable.

[0023]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below.

Example 1 Polycarbonate (Iupilon, manufactured by Mitsubishi Gas Chemical Co., Ltd., 30
100 parts by weight of refractive index at ℃ 1.587) and styrene / ethylene / butadiene / styrene / block copolymer (Tuftec H1051, Asahi Kasei, crumb-shaped, 30
1 part by weight of a refractive index of 1.517) was mixed and kneaded with a twin-screw kneader (manufactured by Toyo Seiki, Labo Plastomill, different direction, resin temperature 180 ° C., screw rotation speed 50 rpm). The torque gradually decreased, became almost constant in 10 minutes from the start of kneading, and further kneaded for 5 minutes to obtain a resin composition.

Example 2 The composition obtained in Example 1 was hot-pressed (resin temperature 180 ° C.).
20 mm × 15 m at 300 ° C., 300 kgf / cm ² , 3 minutes)
A m-thick plate having a thickness of 3.0 mm was formed. This board is transparent,
The haze value was 3.

This plate was sliced to a thickness of about 0.05 μm, the polystyrene portion was stained with ruthenium tetroxide, and observed by a transmission electron microscope. As a result, it was found that the rubbery polymer had a diameter of about 0. It had a substantially spherical microdomain structure of 18 μm.

This plate was heated in boiling water at 100 ° C. for 30 minutes, heated under steam at 121 ° C. for 30 minutes, at 85 ° C./90.
After being left at% RH for 48 hours, the temperature was returned to room temperature, but in any case, no visual change was observed by visual observation and microscopic observation at a magnification of 50 times. The haze value was 3, which was not changed.

Comparative Example 1 A plate was molded in the same manner as in Example 2 except that polycarbonate (Iupilon) was used instead of the resin composition obtained in Example 1. The plate was transparent and had a haze value of 3.

This plate was heated in boiling water at 100 ° C. for 30 minutes, heated under steam at 121 ° C. for 30 minutes, at 85 ° C./90.
After left standing at% RH for 48 hours and then returned to room temperature, white turbidity was visually observed in all cases, and haze value was 10
Met. A disc-shaped crack was recognized by microscopic observation at a magnification of 50 times.

[0030]

From these results, it was found that the resin composition of the present invention suppresses environmental whitening due to disc cracks and the like.

Claims (3)

(57) [Claims] 1. A thermoplastic resin composition in which a rubber-like polymer is dispersed in a thermoplastic resin excluding the thermoplastic norbornene-based resin to form microdomains having a particle size of 0.5 μm or less. 2. A rubbery polymer, the thermoplastic resin composition of claim 1 wherein the rubbery polymer having a glass transition temperature of 40 ° C. or less. 3. A method for suppressing environmental whitening of a thermoplastic resin, wherein a rubbery polymer is dispersed in a thermoplastic resin excluding a thermoplastic saturated norbornene resin so as to form microdomains having a particle size of 0.5 μm or less.