Halogen-free flame resisting synthetic resin composition

Abstract

The present invention relates to a self-fire distinguishable halogen-free flame resisting synthetic resin composition obtained by adding 0.5 to 15 parts by weight of synthetic silicate (also called "hydrated silicic acid" or "wet silica") to 100 parts by weight of a mixture comprising 70 to 30 parts by weight of at least one thermoplastic synthetic resin and 30 to 70 parts by weight of magnesium hydroxide or aluminum hydroxide having an average particle size of 0.1 to 10 .mu.m.This composition is white semitranslucent unlike the one containing carbon black according to the prior art, so that it is suitable for decorative use including floor materials and wall covering materials.

Description

TECHNICAL FIELD

The present invention is appliable to the field of preparing a synthetic resin composition of a flame resisting material.

BACKGROUND ART

Recently, a wide variety of flame resisting synthetic resin compositions have been developed with the purpose of ensuring the safety against a fire. Among them, flame resisting synthetic resin compositions not containing halogen, phosphorus or antimony trioxide, i.e., so-called non-toxic flame resisting synthetic resin compositions of a halogen-free type are given special attention.

Generally, such a flame resisting synthetic resin composition of a halogen-free type contains an inorganic filler such as aluminum hydroxide or magnesium hydroxide. Further, the amount of the inorganic filler required to obtain sufficiently high flame resisting effect is generally 30 to 70% by weight based on the composition. However, a synthetic resin composition containing an inorganic filler in such a high content does not generally exhibit well-balanced strength, so that it is brittle and poor in processability.

Further, some synthetic resin compositions containing such a flame resistant filler alone do not exhibit sufficient flame resistance. Thus the simultaneous addition of such a filler and carbon black has been attempted with the purpose of overcoming these problems (see Japanese Patent Publication No. 10898/1982). The simultaneous addition thereof is known to impart high flame resistance to a synthetic resin, even when the amount of a flame resistant filler is relatively small. However, the halogen-free flame resisting compositions thus prepared are all black, so that they can not be applied to the fields wherein color discrimination is necessitated or the fields wherein importance is attached to appearance, i.e., the fields wherein the use of a black material is unfavorable (for example, wall covering material).

DISCLOSURE OF INVENTION

An object of the present invention is to provide, without using carbon black, a halogen-free flame resisting synthetic resin composition. Thus making it widely appliable to the field wherein a color-discriminable flame reisting composition must be used. In addition to fields wherein importance is attached to appearance, for example, wall covering material.

More particularly, the present invention relates to a self-fire extinguishable, halogen-free and flame resisting synthetic resin composition. This is obtained by adding 0.5 to 15 parts by weight of a synthetic silicate (also called "hydrated silicic acid" or "wet silica") to a mixture comprising 70 to 30 parts by weight of a thermoplastic synthetic resin and 30 to 70 parts by weight of magnesium hydroxide or aluminum hydroxide having an average particle size of 0.1 to 10 .mu.m.

BEST MODE FOR CARRYING OUT THE INVENTION

Synthetic Resin

The synthetic resin to be used in the present invention may be any one as far as it is thermoplastic, and examples thereof include crystalline polyolefins such as polyethylene, ethylene-vinyl acetate copolymer (abbreviated to "EVA"), ethylene-ethyl acrylate copolymer (abbreviated to "EEA"), ethylene-methyl methacrylate copolymer (abbreviated to "EMMA") and polypropylene (abbreviated to "PP"), polystyrene, polyacrylonitrile, acrylonitrile-butadiene-styrene copolymer (abbreviated to "ABS"), nylon-6 and nylon-6,6. It is preferred from the viewpoint of the strength of the resulting composition that the resin have a melt index of 0.2 to 10.0.

Inorganic flame retardant

The inorganic flame retardant to be used in the present invention is aluminum hydroxide or magnesium hydroxide having a particle size of 0.1 to 10 .mu.m.

According to the present invention, such a flame resistant filler may be added in an amount of 30 to 70% by weight based on the composition to thereby impart flame resistant effect to the resin.

Synthetic Silicate

The synthetic silicate to be used in the present invention is generally called "hydrated silicic acid" or "wet silica". Further, it does not have a specified crystalline structure but a network structure of Si-O, so that it is also called "amorphous silica". The synthetic silicate may be any one containing 40 to 70% by weight of SiO.sub.2 as a major component and 10 to 45% by weight of MgO and CaO as secondary components. Particularly, a synthetic silicate containing 50 to 60% by weight of SiO.sub.2 and 12 to 30% by weight of MgO and CaO and having an ignition loss of 10 to 30% by weight is preferred.

Other Additives

Although the composition according to the present invention essentially comprises of a thermoplastic synthetic resin, an inorganic flame retardant as described above and synthetic silicate, it may contain an antioxidant or lubricant for the purpose of enhancing the stability of the composition at processing, or a titanate or silane coupling agent for the purpose of enhancing the adhesion of the filler to the matrix in an arbitrary amount in addition to the above essential components without affecting the effect of the present invention.

Further, the composition of the present invention may also contain an organic or inorganic pigment such as carbon black, azotype pigment, cyanine blue, cyanine green, iron oxide red or titanium oxide for the purpose of coloring.

Function of the Invention

The synthetic silicate, i.e., non-crystalline silica to be used in the present invention has an amorphous steric chain of Si-O-Si-O in its structure. Therefore, it is estimated that when a synthetic silicate having such a structure is added to a halogen-free flame resisting synthetic resin composition containing an inorganic flame retardant as described above, a special flame resistant effect due to the flame resistant properties of the silicate itself and the steric flame resistant network formed in the composition be imparted to the composition. Thus substantially utilizing the generation of water by the decomposition of the inorganic flame retardant and the endothermic effect thereby.

Preparation of the composition of the present invention

The halogen-free flame resisting synthetic resin composition, according to the present invention may be prepared by using a master batch comprising a thermoplastic synthetic resin, an inorganic retardant as described above, synthetic silicate and other additives or by mixing these components each in such an amount as to give its end-use concentration and kneading the obtained mixture by an ordinary means such as single-screw type extruder, twin-screw type extruder, roll mill or Banbury mixer.

Further, synthetic silicate may be preliminarily added as such to the other components to obtain the composition of the present invention. Alternatively, a master batch comprising synthetic silicate and a synthetic resin may be added to a composition comprising a synthetic resin and an inorganic flame retardant as described above to thereby obtain the composition of the present invention.

Evaluation of the Invention

The evaluation of the composition according to the present invention is carried out as follows: Namely, when a thermoplastic resin other than polystyrene or ABS was used, the resin, an inorganic flame retardant and other additives were mixed and the obtained mixture was kneaded in a 75 l. Banbury mixer and processed with a mixing roll to obtain a sheet having a thickness of 3 mm. This sheet was reprocessed with a rectangular pelletizer to obtain a rectangular pellet having a length of each side of about 3 mm.

This rectangular pellet was repelletized with a 70.phi. extruder of a vent type at 150.degree. C. to obtain a cylindrical pellet. This cylindrical pellet was used as a sample.

The cylindrical pellet was examined for oxygen index according to JIS K-7201. Further, the pellet was molded into a sheet having a thickness of 200 .mu.m with a T-die sheet molding machine to determine the combustion rate of the sheet with a flammability tester of FMVSS-302.

When polystyrene or ABS was used as the thermoplastic synthetic resin, the resulting composition was molded with an injection machine of 3.5 ounce into a test bar according to the vertical flame test of UL-94 and the test bar was further molded into a test piece having a thickness of 1/8 inch. This test piece was used as a sample for the vertical flame test.

EXAMPLES AND COMPARATIVE EXAMPLES

The present invention will be described in more detail by referring to the following Examples and Comparative Examples.

The components constituting the composition of each Example or Comparative Example will be described, with the proviso that the amounts thereof used are shown in parts by weight and the comparative results of the compositions are shown in Tables 1 to 3.

EXAMPLE 1

______________________________________low-density polyethylene (YUKARON HE-30 60.0 partsmfd. by Mitsubishi Petrochemical Co., Ltd., MI: 0.3)magnesium hydroxide (KISUMA 5B mfd. by 40.0 partsKyowa Chemicals Co., Ltd., average particlesize: 0.8 .mu.m)synthetic silicate (SILMOS-T mfd. by Shiraishi 3.0 partsIndustrial Co., Ltd., SiO.sub.2 content: 60%)total 103.0 parts______________________________________

EXAMPLE 2

______________________________________low-density polyethylene (the same as that used in 55.0 partsExample 1)magnesium hydroxide (the same as that used 45.0 partsin Example 1)synthetic silicate (the same as that used 3.0 partsin Example 1)total 103.0 parts______________________________________

EXAMPLE 3

______________________________________low-density polyethylene (the same as that used in 50.0 partsExample 1)magnesium hydroxide (the same as that used in 50.0 partsExample 1)synthetic silicate (the same as that used in 1.5 partsExample 1total 101.5 parts______________________________________

EXAMPLE 4

______________________________________low-density polyethylene (the same as that used in 50.0 partsExample 1)magnesium hydroxide (the same as that used in 50.0 partsExample 1)synthetic silicate (the same as that used in 3.0 partsExample 1total 103.0 parts______________________________________

EXAMPLE 5

______________________________________straight-chain low-density polyethylen 50.0 parts(ULTZEX 3520F mfd. by Mitsui PetrochemicalIndustries, Ltd. MI: 2.1)magnesium hydroxide (KX-4S mfd. by Asahi 50.0 partsGlass Co., Ltd., average particle size: 0.6 .mu.m)synthetic silicate (SILMOS-T mfd. by Shiraishi 3.0 partsIndustrial Co., Ltd., SiO.sub.2 content: 60%total 103.0 parts______________________________________

EXAMPLE 6

______________________________________high-density polyethylene (HIZEX 3300F 50.0 partsmfd. by Mitsui Petrochemical Industries, Ltd.,MI: 0.9)magnesium hydroxide (KISUMA 5B, the same 50.0 partsas that used in Example 1)synthetic silicate (SOLEX CM mfd. by 3.0 partsTokuyama Soda Co., Ltd., SiO.sub.2 content: 57%)total 103.0 parts______________________________________

EXAMPLE 7

______________________________________ethylene-vinyl acetate copolymer (Evatate H 50.0 parts1011 mfd. by Sumitomo Chemical Co., Ltd., vinylacetate content: 15%)magnesium hydroxide (KISUMA 5B, the same 50.0 partsas that used in Example 1)synthetic silicate (SOLEX CM, the same 3.0 partsas that used in Example 6)total 103.0 parts______________________________________

EXAMPLE 8

______________________________________polypropylene (JHG mfd. by Mitsui Toatsu 50.0 partsChemicals, Inc., MI: 4.0)magnesium hydroxide (KISUMA 5B, the same 50.0 partsas that used in Example 1)synthetic silicate (SOLEX CM, the same 3.0 partsas that used in Example 6)total 103.0 parts______________________________________

EXAMPLE 9

______________________________________low-density polyethylene (YUKARON HZ-30, 50.0 partsthe same as that used in Example 1)aluminum hydroxide (HIGILITE H-42M mfd. by 50.0 partsShowa Light Metal Co., Ltd., average particlesize: 0.8 .mu.m)synthetic calcium silicate (SOLEX CM, the 3.0 partssame as that used in Example 6)total 103.0 parts______________________________________

EXAMPLE 10

______________________________________low-density polyethylene (YUKARON HZ-30, thesame as that used in Example 1) 50.0 partsmagnesium hydroxide (KISUMA 5B, the same as that usedin Example 1) 50.0 partssynthetic calcium silicate (SILMOS-T, the same as thatused in Example 1) 7.0 partstotal 107.0 parts______________________________________

EXAMPLE 11

______________________________________low-density polyethylen (YUKARON HZ-30, thesame as that used in Example 1) 50.0 partsaluminium hydroxide (HIGILITE H-42M mfd. byShowa Light Metal Co., Ltd., average particlesize of 0.8 .mu.m) 50.0 partssynthetic calcium silicate (SILMOS-T,the same as that used in Example 1) 10.0 partstotal 110.0 parts______________________________________

EXAMPLE 12

______________________________________polystyrene (STYRON 470 mfd. by Asahi ChemicalIndustry Co., Ltd., MI:4.0) 50.0 partsmagnesium hydroxide (KISUMA 5B, the same asthat used in Example 1) 50.0 partssynthetic calcium silicate (SILMOS-T,the same as that used in Example 1) 3.0 partstotal 103.0 parts______________________________________

EXAMPLE 13

______________________________________ABS (DENKA OF mfd. by Denki KagakuKogyo K.K.) 50.0 partsmagnesium hydroxide (KISUMA 5B, the same asthat used in Example 1) 50.0 partssynthetic calcium silicate (SILMOS-T,the same as that used in Example 1) 3.0 partstotal 103.0 parts______________________________________

COMPARATIVE EXAMPLE 1

______________________________________low-density polyethylene (YUKARON HZ-30mfd. by Mitsubishi Petrochemical Co., Ltd., MI:0.3) 60.0 partsmagnesium hydroxide (KISUMA 5B, mfd. by KyowaChemicals Co., Ltd., average particle size: 0.8 .mu.m) 40.0 partstotal 100.0 parts______________________________________

COMPARATIVE EXAMPLE 2

______________________________________low-density polyethylene (the same as that used inComparative Example 1) 55.0 partsmagnesium hydroxide (the same as that used inComparative Example 1) 45.0 partstotal 100.0 parts______________________________________

COMPARATIVE EXAMPLE 3

______________________________________low-density polyethylene (the same as that used inComparative Example 1) 50.0 partsmagnesium hydroxide (the same as that used inComparative Example 1) 50.0 partstotal 100.0 parts

COMPARATIVE EXAMPLE 4

______________________________________straight-chain low-density polyethylene(ULTZEX 2020L mfd. by Mitsui PetrochemicalIndustries, Ltd., MI:2.1) 50.0 partsmagnesium hydroxide (the same as that used inComparative Example 1) 50.0 partstotal 100.0 parts______________________________________

COMPARATIVE EXAMPLE 5

______________________________________high-density polyethylene (HIZEX 3300F mfd. byMitsui Petrochemical Industries, Ltd., MI:0.9) 50.0 partsmagnesium hydroxide (the same as that used inComparative Example 1) 50.0 partstotal 100.0 parts______________________________________

COMPARATIVE EXAMPLE 6

______________________________________low-density polyethylene (the same as that used inComparative Example 1) 50.0 partsmagnesium hydroxide (the same as that used inComparative Example 1) 50.0 partscrystalline silica (TOKUSIL U mfd. by TokuyamaSoda Co., Ltd., SiO.sub.2 content: 95%) 3.0 partstotal 103.0 parts______________________________________

COMPARATIVE EXAMPLE 7

______________________________________low-density polyethylene (the same as that used inComparative Example 1) 50.0 partsmagnesium hydroxide (the same as that used inComparative Example 1) 50.0 partsmica (Mica #300 mfd. by Repco, average particlesize: 2 .mu.m) 3.0 partstotal 103.0 parts______________________________________

COMPARATIVE EXAMPLE 8

______________________________________low-density polyethylene (the same as that used inComparative Example 1) 50.0 partsmagnesium hydroxide (the same as that used inComparative Example 1) 50.0 partscalcium magnesium carbonate (Pigment white 18Amfd. by Shiraishi Industrial Co., Ltd., averageparticle size: l .mu.m) 3.0 partstotal 103.0 parts______________________________________

COMPARATIVE EXAMPLE 9

______________________________________low-density polyethylene (the same as that used inComparative Example 1) 50.0 partsmagnesium hydroxide (the same as that used inComparative Example 1) 50.0 partscarbon black (Mitsubishi MB #30 mfd. byMitsubishi Chemical Industries, Ltd.) 3.0 partstotal 103.0 parts______________________________________

COMPARATIVE EXAMPLE 10

______________________________________polystyrene (STYRON 470 mfd. by Asahichemical Industry Co., Ltd., MI: 4.0) 50.0 partsmagnesium hydroxide (the same as that used inComparative Example 1) 50.0 partstotal 100.0 parts______________________________________

COMPARATIVE EXAMPLE 11

______________________________________ABS (DENKA OF mfd. by Denki Kagaku KogyoK.K.) 50.0 partsmagnesium hydroxide (the same as that used inComparative Example 1) 50.0 partstotal 100.0 parts______________________________________ TABLE 1______________________________________Results of Examples using crystalline olefin Flame Oxy- combustion Synthetic resistant gen rateNo. resin filler Additive index (mm/min)______________________________________Ex. 1 60.0 40.0 3.0 24.0 68.0 LDPE Mg(OH).sub.2 SILMOS-TEx. 2 55.0 45.0 3.0 27.0 46.0 LDPE Mg(OH).sub.2 SILMOS-TEx. 3 50.0 50.0 1.5 29.2 o LDPE Mg(OH).sub.2 SILMOS-TEx. 4 50.0 50.0 3.0 30.4 o LDPE Mg(OH).sub.2 SILMOS-TEx. 5 50.0 50.0 3.0 30.2 o LDPE Mg(OH).sub.2 SILMOS-TEx. 6 50.0 50.0 3.0 29.6 o HDPE Mg(OH).sub.2 SOLEX CMEx. 7 50.0 50.0 3.0 30.4 o EVA Mg(OH).sub.2 SOLEX CMEx. 8 50 0 50.0 3.0 29.8 o PP Mg(OH).sub.2 SOLEX CMEx. 9 50.0 50.0 3.0 29.4 o LDPE Al(OH).sub.3 SOLEX CMEx. 10 50.0 50.0 7.0 30.0 o LDPE Mg(OH).sub.2 SILMOS-TEx. 11 50.0 50.0 10.0 29.8 o LDPE Al(OH).sub.3 SILMOS-T______________________________________ TABLE 2______________________________________Results of Comparative Examples usingcrystalline olefin Flame Combustion Synthetic resistant Oxygen rateNo. resin filler Additive index (mm/min)______________________________________Comp. 60.0 40.0 -- 22.4 180.0Ex. 1 LDPE Mg(OH).sub.2Comp. 55.0 45.0 -- 24.2 78.0Ex. 2 LDPE Mg(OH).sub.2Comp. 50.0 50.0 -- 25.2 76.0Ex. 3 LDPE Mg(OH).sub.2Comp. 50.0 50.0 -- 24.8 84.0Ex. 4 LDPE Mg(OH).sub.2Comp. 50.0 50.0 -- 25.4 80.0Ex. 5 HDPE Mg(OH).sub.2Comp. 50.0 50.0 3.0 25.6 67.0Ex. 6 LDPE Mg(OH).sub.2 crystalline silicaComp. 50.0 50.0 3.0 25.2 73.0Ex. 7 LDPE Mg(OH).sub.2 micaComp. 50.0 50.0 3.0 25.0 81.0Ex. 8 LDPE Mg(OH).sub.2 carbonateComp. 50.0 50.0 3.0 29.4 oEx. 9 LDPE Mg(OH).sub.2 carbon black______________________________________ (note) LDPE refers to lowdensity polyethylene, HDPE refers to highdensity polyethylene and EVA refers to ethylenevinyl acetate copolymer. The symbo "o" in the column of combustion rate means that the test sheet or test piece did not burn up to the mark, i.e., that the test sheet or test piec was selffire extinguishable. TABLE 3______________________________________Examples and Comparative Examples usingstyrenic resin Flame Synthetic resistant Oxygen UL 94No. resin filler Additive index (1/8")______________________________________Ex. 12 50.0 50.0 3.0 29.0 V-1 PS Mg(OH).sub.2 SILMOS-TEx. 13 50.0 50.0 3.0 29.4 V-1 ABS Mg(OH).sub.2 SILMOS-TComp. 50.0 50.0 -- 26.0 HBEx. 10 PS Mg(OH).sub.2Comp. 50.0 50.0 -- 25.6 HBEx. 11 ABS Mg(OH).sub.2______________________________________ (note) PS refers to polystyrene. "V-1" means that the flame of the test piece guttered out within 30 seconds after contacting the test piece with flame. "HB" means that the test is did not burn until the mark in the horizontal flame test, though the test piece did not fit the vertical flame test.

INDUSTRIAL APPLICABILITY

According to the present invention, a white semi-translucent synthetic resin composition which is highly flame resistant and does not generate any toxic substance can be obtained, though such a composition can not be obtained according to the prior art. The flame resisting synthetic resin composition of the present invention will be able to be used in a wide field requiring color discrimination, for example, floor materials of a nuclear power station.

Claims

1. A self-extinguishing, halogen-free flame retardant composition comprising 70 to 30 parts by weight of at least one thermoplastic synthetic resin, 30-70 parts by weight of magnesium hydroxide having an average particle size of 0.1 to 10 .mu.m, and 0.5-15 parts by weight of a synthetic silicate which is a non-crystalline silica having an amorphous steric chain of Si-O-Si-O in its structure.

2. The composition as defined by claim 1 wherein said at least one thermoplastic resin is selected from the group consisting of low-density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, polypropylene, polystyrene, polyacrylonitrile, acrylonitrile-butadiene-styrene copolymer, nylon 6, and nylon-6,6.

3. The composition as defined by claim 1 wherein said thermoplastic synthetic resin has a melt index of 0.2 to 10.0.

4. The composition as defined by claim 1 wherein said synthetic silicate comprises 40 to 70% by weight SiO.sub.2 and 10 to 45% by weight MgO and CaO.

5. The composition as defined by claim 4 wherein said synthetic silicate comprises 50 to 60% by weight SiO.sub.2, 12 to 30% by weight MgO and CaO, and an ignition loss of 10 to 30% by weight.

6. The composition as defined by claim 1 wherein the sum of said thermoplastic synthetic resin and said magnesium hydroxide equals 100 parts by weight.

7. A self-extinguishing, halogen-free, flame retardant composition comprising 70 to 30 parts by weight of at least one thermoplastic synthetic resin, 30-70 parts by weight of magnesium hydroxide having an average particle size of 0.6 to 0.08 .mu.m, and 0.5-15 parts by weight of a synthetic silicate salt.

8. The composition as defined by claim 7 wherein said at least one thermoplastic resin is selected from the group consisting of low-density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, polypropylene, polystyrene, polyacrylonitrile, acrylonitrile-butadiene-styrene copolymer, nylon 6, and nylon-6,6.

9. The composition as defined by claim 7 wherein said thermoplastic synthetic resin has a melt index of 0.2 to 10.0.

10. The composition as defined by claim 7 wherein said synthetic silicate comprises 40 to 70% by weight SiO.sub.2 and 10 to 45% by weight MgO and CaO.

11. The composition as defined by claim 10 wherein said synthetic silicate comprises 50 to 60% by weight SiO.sub.2, 12 to 30% by weight MgO and CaO, and an ignition loss of 10 to 30% by weight.

12. The composition as defined by claim 7 wherein the sum of said thermoplastic synthetic resin and said magnesium hydroxide equals 100 parts by weight.