KR19990083193A - Thermoplastic resin composition and refrigerator gasket - Google Patents

Abstract

The present invention has a good secondary processing such as heat welding, there is no gloss on the surface of the molded article, and flexible and less sticky, giving a molded article having a good appearance with a wide range of balanced extrusion process conditions such as strength, abrasion resistance, and oil resistance. Provided is a thermoplastic resin composition. That is, the present invention is a combination of (a) polypropylene, (b) hydrogenated block copolymer, (c) dynamic or static vulcanized ethylene-α-olefin copolymer rubber and polyolefin resin, Alternatively, a thermoplastic elastomer comprising a mixture of ethylene-α-olefin-non-conjugated diene copolymer rubber and polyolefin resin vulcanized dynamically or statically, and (d) a thermoplastic resin composition comprising paraffinic process oil softener and a refrigerator gasket using the same do.

Description

Thermoplastic Composition and Refrigerator Gaskets {THERMOPLASTIC RESIN COMPOSITION AND REFRIGERATOR GASKET}

In the present invention, the secondary processing such as heat welding is good, so that the surface of the molded product is not glossy, and it is flexible and less sticky, thereby providing a molded product having a wide range of balanced extrusion molding conditions such as strength, abrasion resistance, oil resistance, and the like. It relates to a thermoplastic resin composition.

In general, since non-halogen thermoplastic resin is a non-polar resin, there is a problem in that secondary processing such as thermal welding cannot be processed equally to halogen-based resin. As a result, non-halogen resins have large restrictions on their use and often fail to proceed as a substitute for halogen-based resins, which have been pointed out as environmental problems.

Particularly, soft vinyl chloride resin (PVC) has been conventionally used for refrigerator gaskets, but foodstuffs are stored in the refrigerator, and vinyl chloride resin, which is a problem due to environmental hormones, has become a problem for the environment. In addition, when the refrigerator is closed, halogens are contained in the vinyl chloride, so there is a problem such as dioxin, and thus there is a problem that it cannot be easily incinerated.

In order to solve these problems, examination is made as resin which does not use vinyl chloride. However, due to the disadvantages of wear resistance, insufficient heat adhesion of the corner portion, and adhesiveness of the surface, the replacement of the refrigerator gasket formed of vinyl chloride resin was not advanced.

An object of the present invention is to provide a good molded article having a wide range of extruded processing conditions such as strength, abrasion resistance, oil resistance, etc., because the secondary processing such as heat welding is good and the surface of the molded product is not glossy and less sticky. It is to provide a halogen thermoplastic resin composition.

In addition, a second object of the present invention is to provide a refrigerator gasket formed of a resin that does not contain halogens having the same characteristics as conventional refrigerator gaskets formed of a vinyl chloride resin and not causing environmental problems such as environmental hormones and dioxins. .

The present invention (a) melt flow rate (hereinafter referred to as MFR: conditions of ASTM-D-1238L, 230 ℃, the same conditions below) 15 to 21% by weight of polypropylene of 0.5 to 10g / 10 minutes,

(b) having at least one polymer block A mainly composed of vinyl aromatic compounds and at least one polymer block B mainly composed of conjugated diene compounds, and having a vinyl aromatic compound content of 5 to 50% by weight. 70% or more of the conjugated diene compound portion is hydrogenated, and the number average molecular weight is 100,000 to 200,000 hydrogenated block copolymer 25 to 41% by weight,

(c) a mixture of dynamically or statically vulcanized ethylene-α-olefin copolymer rubber and polyolefin resin, or a mixture of dynamically or staticly vulcanized ethylene-α-olefin-non-conjugated diene copolymer rubber and polyolefin resin Len insoluble content (elution condition; after distillation at 120 ° C. × 20 hours, filtered through 100 mesh to obtain a percentage by dividing 100 mesh residue by the total weight before deposition; hereafter referred to as gel fraction) 12-12 thermoplastic elastomers having 30-50 wt% 22 weight percent, and

(d) It is a thermoplastic resin composition which consists of 26-38 weight% of paraffin type process oil softener whose viscosity (40 degreeC) is 300-500 centistokes and an aniline point is 130-160 degreeC.

Moreover, it is a refrigerator gasket using the said thermoplastic resin composition.

The polypropylene (a) in the resin composition gives good appearance and heat resistance to the obtained composition. The kind of polypropylene is not specifically limited, A homo polypropylene, random polypropylene, or block polypropylene may be sufficient. Among them, homopolypropylene is good in terms of heat resistance. The polypropylene has an MFR of 0.5 to 10 g / 10 minutes, and when the MFR is less than 0.5 g / 10 minutes, the fluidity of the whole composition is lowered, resulting in poor moldability. If the content exceeds 10g / 10min, the hydrogenated block copolymer becomes poor in dispersion, which may cause protrusions or unstable physical properties, which is undesirable. Preferably it is 1-10 g / 10min.

In addition, the addition amount is 15-21 weight% with respect to the resin composition. If it is less than 15% by weight, the flowability of the entire resin composition is lowered, so that moldability is deteriorated. If it exceeds 21% by weight, it is not preferable because the flexibility is impaired.

If necessary, a polypropylene containing a nucleating agent, an antistatic agent and a weathering stabilizer may be used as long as the above properties are not impaired.

The hydrogenated block copolymer (b) in the resin composition has at least one polymer block A mainly composed of vinyl aromatic compounds and at least one polymer block B mainly composed of conjugated diene compounds. It is in the range of 5 to 50% by weight, and at least 70% of the conjugated diene compound portion is hydrogenated.

In this hydrogenated block copolymer, styrene, (alpha) -methylstyrene, o, m and p-methylstyrene, 1, 3- dimethyl styrene, vinyl naphthalene, vinyl anthracene etc. are mentioned as a vinyl aromatic compound. And Polymer block A is a polymer consisting of homopolymers or mixtures thereof.

The conjugated diene compound is 1,3-butadiene, isoplan, 2,3-dimethyl-1,3butadiene, 1,3-pentadiene, 1,3-hexadiene and the like, and the polymer block B is a homopolymer thereof or these It is a polymer consisting of a mixture of.

The content of the vinyl aromatic compound in the hydrogenated block copolymer is 5 to 50% by weight. When the content rate of the vinyl aromatic compound is out of this range, the rigidity of the whole composition becomes high and it becomes impossible to maintain flexibility.

The number average molecular weight (Mn) of the hydrogenated block copolymer is in the range of 100,000 to 200,000, preferably 130,000 to 200,000, and the molecular weight distribution (Mw / Mn) is preferably 10 or less (Mw: weight average molecular weight), and preferably 5 or less and most preferably 2 or less. If the number average molecular weight is less than 100,000, sufficient oil resistance cannot be given. In addition, when the number average molecular weight exceeds 200,000, fluidity is extremely lowered and molding cannot be performed.

In addition, the hydrogenated block polymer is hydrogenated at least 70% of the conjugated diene portion. If the hydrogenation amount of the conjugated diene portion is less than 70%, the weather resistance is extremely weakened, which causes a great restriction in use, which is undesirable. The structure of the hydrogenated block copolymer may be either linear or branched.

Moreover, the hydrogenated block copolymer used for this invention may further modify this, ie, may provide polar groups, such as a hydroxyl group, a carboxyl group, and an epoxy group, in a molecular terminal or molecular chain.

The amount of the hydrogenated block copolymer added is 25 to 41 wt% based on the resin composition. Exceeding 41% by weight results in extremely poor fluidity. If it is less than 25 wt%, oil resistance is impaired. Preferably it is 27-33 weight%.

As a blend of the dynamic or statically vulcanized ethylene-α-olefin copolymer rubber and polyolefin resin used in the present invention, or a blend of the dynamic or static vulcanized ethylene-α-olefin-non-conjugated diene copolymer rubber and polyolefin resin. The thermoplastic elastomer (c) having a xylene insoluble content of 30 to 50% by weight greatly contributes to the improvement of the heat welding property and the formability, and also has a feature very similar to that of the halogen resin surface.

In the copolymer rubber, the α-olefin preferably has 3 to 15 carbon atoms. As the non-conjugated diene, dicyclopentadiene, 1,4-hexadiene, ethylidene norbornene, methylene norbornene and the like can be used. In the present invention, polypropylene is preferable as the? -Olefin from the viewpoints of availability and improved heat resistance characteristics. Therefore, EPDM is suitable as a rubber component. The ethylene / α-olefin ratio of the two kinds of copolymer rubbers is preferably 50/50 to 90/10 by weight ratio, more preferably 60/40 to 80/20. Examples of the polyolefin resins include polyethylene, polypropylene, ethylene propylene copolymers and mixtures thereof, but polypropylene is preferred.

As a vulcanizing agent, a vulcanizing agent for rubber can be used. In particular, organic peroxides such as alkylphenol / formaldehyde resins and dimcyl peroxide are particularly suitably used in addition to sulfur. In addition to the vulcanizing agent, a vulcanizing aid, an antioxidant, or the like may be used in combination. The addition amount of the alkylphenol formaldehyde resin is preferably in the range of 0.5 parts by weight to 15 parts by weight based on 100 parts by weight of the copolymer rubber in view of the balance between strength and workability. In the case of an organic peroxide, the range of 0.05 weight part-1 weight part with respect to 100 weight part of copolymer rubbers is preferable at the point of strength and workability. It is indispensable to contain 5 weight part or more of polyolefin resins with respect to 100 weight part of copolymer rubbers in order to maintain workability. The present component (c) can be obtained by vulcanization by adding a vulcanizing agent without dynamically kneading kneaded copolymer copolymer and polyolefin resin or by dynamically melting and kneading.

The gel fraction of component (c) (elution condition; filtered through 100 mesh after 120 ° C. x 20 hours immersion in xylene and the percentage obtained by dividing 100 mesh residue by the total weight before deposition) is 30-50% by weight. . If the gel fraction is less than 30% by weight, the heat weldability of the corner portion is insufficient, and if it exceeds 50% by weight, the wear resistance rapidly decreases and an undesirable state occurs.

The compounding quantity of component (c) is 12 to 22 weight% with respect to a resin composition, Preferably it is 16 to 20 weight%. If it is less than 12% by weight, the heat weldability is insufficient, and the adhesion of the surface by the oil used as the softener cannot be suppressed, and the adhesion on the external surface of the molded article is large, which is not preferable. Moreover, when it exceeds 22 weight%, there exists a fault that the intensity | strength falls extremely and abrasion resistance falls.

The softener (d) in the resin composition has a property of softening the composition to impart fluidity. As the type of softener, it is necessary to use a paraffinic process oil suitable for compatibility, and have a viscosity (40 ° C) of 300 to 500 centistokes and aniline point of 130 to 160 ° C in terms of bleeding. The addition amount needs to be 26 to 38 weight% in terms of fluidity, softening effect, and stickiness of the bleed surface. Preferably it is 30-34 weight%.

In addition, an inorganic filler, a nucleating agent, an external agent, an anti-oxidant, a light stabilizer, an ultraviolet absorber, an antioxidant, a colorant, and a surface modifier may be added to the composition as necessary.

As a method for producing the composition of the present invention, all the usual methods used for the production of ordinary resin compositions and rubber compositions can be adopted. Basically, it is a mechanical melt kneading method, and a single screw extruder, a twin screw extruder, a Banbury-mixer, various kneaders, a brushbender, a roll, and the like are used. At this time, the temperature for melt kneading can be preferably selected in the range of 180 to 300 ° C.

Since the composition obtained here is thermoplastic, it is possible to shape | mold using the thermoplastic resin molding machine generally used.

In addition, the composition obtained here can be molded into a refrigerator gasket by an extruder which is usually used as a vinyl chloride resin. The molded product obtained by extrusion molding is cut to a suitable size, and a magnet is inserted into a pocket of the side contacting the refrigerator iron plate, and a small amount of foam is inserted into the corner portion to thermally weld the corner portions to obtain a refrigerator gasket. Can be.

The present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Examples 1-2 and Comparative Examples 1-14

Each component mix | blended in an Example and a comparative example is as follows.

<Component a (1)> Polypropylene manufactured by Nippon Polyolefin Co., Ltd. (MFR = 1 g / 10 min)

<Component a (2)> Polypropylene manufactured by Nippon Polyolefin Co., Ltd. (MFR = 15 g / 10 min)

<Component b (1)> Hydrogenated block copolymer having a polystyrene-hydrogenated polybutadiene-polystyrene structure manufactured by Asahi Kasei Kogyo Co., Ltd. (styrene content: 30% by weight, hydrogenation rate: 70% or more, number average molecular weight 120,000)

<Component b (2)> Hydrogenated block copolymer having a polystyrene-hydrogenated polybutadiene-polystyrene structure manufactured by Asahi Kasei Kogyo Co., Ltd. (styrene content: 30% by weight, hydrogenation rate: 70% or more, number average molecular weight 60,000)

<Component b (3)> Hydrogenated block copolymer having a structure of polystyrene-hydrogenated polyisoprene-polystyrene manufactured by Clare Corporation (styrene content: 30% by weight, hydrogenation rate: 70% or more, number average molecular weight 170,000)

<Component b (4)> Hydrogenated block copolymer having polystyrene-hydrogenated polyisoprene-polystyrene structure manufactured by Clare Corporation (styrene content: 30% by weight, hydrogenation: 70% or more, number average molecular weight 80,000)

<Component c (1)> Nippon Sego Rubber Co., Ltd. ethylene propylene copolymer (gel fraction 0 weight%)

<Component c (2)> Thermoplastic elastomer dynamically vulcanized with ethylene propylene nonconjugated diene copolymer rubber, polypropylene resin, and friend body by organic peroxide (gel fraction 42% by weight)

<Component d (1)> Paraffin-based process oil manufactured by Idemisuksan Co., Ltd. (viscosity (40 ° C) = 382 centistox, aniline point = 144 ° C)

<Component d (2)> Paraffin-based process oil manufactured by Idemisuksan Co., Ltd. (viscosity (40 ° C) = 96 centistox, aniline point = 128 ° C)

<Component d (3)> Naphthenic process oil manufactured by Idemisuksan Co., Ltd. (viscosity (40 degreeC) = 238 centistox, aniline point = 90 degreeC)

(A) to (d) of the above components were kneaded at a kneading temperature of 220 ° C. as a Banbury mixer, and the kneaded product was passed through a roll to form a thin sheet. This was pulverized with a grinder to obtain pellets of a rectangular thermoplastic resin composition.

This was molded using a ø50 mm extruder to obtain a refrigerator gasket through each step of cut, magnet insert, foam insert, and corner heat welding. Then, the predetermined test piece is cut out and the item evaluation shown below is performed.

(1) Tensile strength: Conforms to JISK 6301 (tension rate 200 mm / min)

Evaluation Symbol and Criteria 1

○: 10 Mpa or more

×: less than 10 Mpa

(2) Formability and Appearance:

The extrudeability and the appearance of this surface characteristic were evaluated by visual observation and touch as a ø50 mm extruder.

Evaluation Symbol and Criteria 2

(Circle): There is no stickiness on the surface, there is no fault by a large foreign material, etc., and it can shape | mold similarly to soft PVC.

X: There is a flaw with stickiness on the surface, or there is a defect with large foreign matter, or it cannot be molded equivalent to soft PVC.

(3) Flexibility: Hardness: JIS K6301 (JIS A type, value after 5 seconds)

Evaluation Symbol and Criteria 3

○: less than 80

×: 80 or more

(4) Heat Weldability of Corner

After molding together with each other by extrusion, the weld strength was calculated as a percentage by comparing the weld strength of the conventional vinyl chloride resin with 90 ° peel test after a heat treatment was performed at 200 ° C. for about 1 to 2 minutes.

Evaluation Symbol and Criteria 4

○: PVC welding strength ratio over 60%

×: PVC welding strength ratio less than 60%

(5) Oil resistance: It is soaked in soybean oil and left for 40 ° C for 48 hours. The weight change rate after that was calculated | required.

Evaluation Symbols and Criteria 5

○: less than 10% weight change

×: 10% or more of weight change rate

(6) Breeding characteristics: The surface state of the specimens after the accelerated weathering test (sunshine shine, black panel temperature 63 ° C., rain x 300 hours) was observed.

Evaluation Symbols and Criteria 6

○: no brid

×: with brid

(7) Refrigerator opening and closing test: A gasket is attached to the refrigerator and subjected to 200,000 opening and closing tests at a rate of 10,000 times / day.

Evaluation Symbols and Criteria 7

(Circle): No abnormality by opening and closing test of 200,000 times.

X: The disadvantages, such as a fracture, were confirmed.

-: Unrated because it could not be molded due to poor molding.

These results are shown in Tables 1-3.

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Formulation Composition wt.% Ingredient a (1) 18 18 14 22 20 15 Component b (1) 33 35 31 24 42 Component b (3) 33 Component c (2) 17 17 17 17 17 17 Component d (1) 32 32 34 30 39 26 Evaluation results Corner weldability ○ ○ ○ ○ ○ ○ Formability, appearance ○ ○ × ○ ○ × flexibility ○ ○ ○ × ○ ○ The tensile strength ○ ○ ○ ○ ○ ○ Breed Castle ○ ○ ○ ○ ○ ○ Oil resistance ○ ○ ○ ○ × ○ Refrigerator opening test ○ ○ ― × × ―

Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Formulation Composition wt.% Ingredient a (1) 18 18 18 18 Component b (1) 36 30 38 30 Component b (3) Component c (2) 11 23 19 13 Component d (1) 35 29 25 39 Evaluation results Corner weldability × ○ ○ ○ Formability, appearance × ○ × × flexibility ○ ○ ○ ○ The tensile strength ○ × ○ ○ Breed Castle ○ ○ ○ ○ Oil resistance ○ ○ ○ ○ Refrigerator opening test ― × ― ―

Comparative Example 9 Comparative Example 10 Comparative Example 11 Comparative Example 12 Comparative Example 13 Comparative Example 14 Formulation Composition wt.% Ingredient a (1) 18 18 18 18 18 Component a (2) 18 Component b (1) 33 33 33 33 Component b (2) 33 Component b (4) 33 Component c (1) 17 Component c (2) 17 17 17 17 17 Component d (1) 32 32 32 32 Component d (2) 32 Component d (3) 32 Evaluation results Corner weldability ○ ○ ○ × ○ ○ Formability, appearance × ○ ○ × × × flexibility ○ ○ ○ ○ ○ ○ The tensile strength ○ × × ○ ○ ○ Breed Castle ○ ○ ○ ○ × × Oil resistance ○ × × ○ ○ ○ Refrigerator opening test ― × × ― ― ―

The present invention is a non-halogen thermoplastic that has a good secondary process such as heat welding and has no gloss on the surface of the molded article, and has a flexible and less sticky appearance, thus providing a molded article having a good appearance with a wide range of balanced processing conditions such as strength and oil resistance. The resin composition can be obtained, in particular, a refrigerator gasket having the same characteristics as a refrigerator gasket conventionally molded with vinyl chloride resin and corresponding to environmental problems can be obtained.

Claims (2)

(a) 15 to 21% by weight of polypropylene having a melt flow rate of 0.5 to 10 g / 10 minutes, (b) one or more polymer blocks (A) mainly composed of vinyl aromatic compounds, and one or more polymer blocks (B) mainly composed of conjugated diene compounds, and the content of vinyl aromatic compounds is 5 to 50; 70% or more of the conjugated diene compound portion is hydrogenated, and the number average molecular weight is from 25 to 41% by weight of a hydrogenated block copolymer of 100,000 to 200,000, (c) Blends of dynamically or statically vulcanized ethylene-α-olefin copolymer rubbers and polyolefin resins, or dynamically or staticly vulcanized ethylene-α-olefin-non-conjugated diene copolymer rubbers and polyolefin resins 12 to 22% by weight of thermoplastic elastomer having a xylene insoluble content of 30 to 50% by weight, and (d) A thermoplastic resin composition comprising 26 to 38 wt% of a paraffinic process oil softener having a viscosity (40 ° C) of 300 to 500 centistokes and an aniline point of 130 to 160 ° C. A refrigerator gasket using the thermoplastic resin composition according to claim 1.