Flame retardant for plastics

Abstract

This flame retardant for plastics comprises any of a thermally depolymerizable polymer to which a water-soluble functional group, e.g., a carboxylic acid group or a sulfonic acid group, has been imparted, an alkali metal salt of the thermally depolymerizable polymer, and an alkaline-earth metal salt of the thermally depolymerizable polymer. Poly(methacrylic acid), for example, is preferred as the thermally depolymerizable polymer having a structure to which a water-soluble functional group has been imparted. Such flame retardant for plastics contains neither a halogen nor nitrogen nor phosphorus in the molecule and can suitably make general-purpose plastics flame-retardant.

Description

Flame retardant for plastics

[0001] The present invention relates to a novel non-PFAS, non-halogen-based flame retardant for plastics, and more particularly to a flame retardant for plastics suitable for flame retarding general-purpose plastics such as polypropylene (PP), polystyrene (PS), and polyphenylene oxide (PPO).

[0002] Until now, flame retardants used in plastics have included chlorine, bromine and other halogenated compounds, phosphorus compounds, nitrogen compounds, and inorganic compounds such as antimony and boron. Recently, regulations on flame retardancy of plastics have been strengthened for safety reasons, and flame retardants containing bromine and chlorine are being particularly restricted because they generate toxic gases when plastics burn.

[0003] While various flame retardants have been considered as substitutes for halogen-based flame retardants for plastics, there has been no conventional flame retardant that does not contain not only halogens but also nitrogen and phosphorus in its molecule, and that can suitably flame retard common plastics such as polypropylene (PP), polystyrene (PS), and polyphenylene oxide (PPO).

[0004] The present invention has been made in view of the above problems, and aims to provide a flame retardant for plastics that does not contain halogens, nitrogen, or phosphorus in its molecule, and is capable of suitably flame-retarding general-purpose plastics such as polypropylene (PP), polystyrene (PS), and polyphenylene oxide (PPO).

[0005] To solve the above problems, the present invention provides a flame retardant for plastics comprising a thermally depolymerizable polymer having a structure to which water-soluble functional groups are attached, an alkali metal salt thereof, or an alkaline earth metal salt thereof (Invention 1).

[0006] In the above invention (Invention 1), it is preferable that the pyropolymerizable polymer having the water-soluble functional group attached has the structure shown in the following chemical formula. (Invention 2) (In the formula, X is hydrogen (H) or an alkyl group having 1 to 3 carbon atoms, and Y is COOH or SO ３ H, OCOOH, OSO ３ H, COO (CH2)ｍ COOH, COO(CH2) ｍ SO ３ H, benzene ring-COOH or benzene ring-SO ３ H is a positive integer between 5 and 27,000, and m is a positive integer between 1 and 5.

[0007] In the above invention (Invention 1), it is preferable that the alkali metal salt is a K salt or a Na salt (Invention 3).

[0008] In the above invention (Invention 1), it is preferable that the alkaline earth metal salt is a Ca salt or a Mg salt (Invention 4).

[0009] In the above inventions (Inventions 1 to 4), it is preferable that the pyropolymer with the structure to which the water-soluble functional group is attached is poly(methacrylic acid) (Invention 5).

[0010] According to these inventions (Inventions 1 to 5), plastics can be effectively made flame-retardant by the effect of polymers in which water-soluble functional groups such as carboxylic acid groups and sulfonic acid groups are attached to a thermally depolymerizable polymer.

[0011] According to the flame retardant for plastics of the present invention, since it consists of a thermally depolymerizable polymer having a structure to which water-soluble functional groups are attached, an alkali metal salt thereof, or an alkaline earth metal salt thereof, it can effectively make plastics flame retardant.

[0012] The flame retardant for plastics of the present invention will be described in detail based on the following embodiments.

[0013] [Plastic Materials] There are no particular restrictions on the plastic materials to which the flame retardant for plastics of this embodiment can be applied, but thermoplastic resins are preferred because it is easy to add the flame retardant for plastics, and general-purpose plastic materials such as polyolefins such as polypropylene (PP) and polyethylene (PE), polystyrene (PS), and polyphenylene oxide (PPO) are particularly suitable.

[0014] [Flame Retardant for Plastics] The flame retardant for plastics of this embodiment is composed of a polymer having a structure in which a water-soluble functional group such as a carboxylic acid group or a sulfonic acid group is imparted to a thermally depolymerizable polymer, an alkali metal salt thereof, or an alkaline earth metal salt thereof.

[0015] The thermally depolymerizable polymer having a structure to which this water-soluble functional group is imparted preferably has a structure represented by the following chemical formula. (In the formula, X is hydrogen (H) or an alkyl group having 1 to 3 carbon atoms, Y is COOH, SO ３ H, OCOOH, OSO ３ H, COO(CH2)mCOOH, COO(CH2)mSO ３ H, benzene ring - COOH or benzene ring - SO ３ H, n is a positive integer of 4 to 27,000, and m is a positive integer of 1 to 5.)

[0016] As the thermally depolymerizable polymer having a structure to which such a water-soluble functional group is imparted, poly(methacrylic acid) can be preferably used.

[0017] Further, as the alkali metal salt of the thermally depolymerizable polymer having a structure to which a water-soluble functional group is imparted, a sodium (Na) salt, a potassium (K) salt, etc. can be used. Further, as the alkaline earth metal salt, a calcium (Ca) salt, a magnesium (Mg) salt, etc. can be used.

[0018] These polymer components preferably have a weight average molecular weight (MW) of 2,000,000 or less, particularly 1,000,000 or less. There is no particular limitation on the lower limit of the weight average molecular weight (MW) as long as it is in the form of a polymer, but it may be 1,000 or more.

[0019] The flame retardant for plastics in this embodiment should be added in an amount of 1 to 30 parts by weight, particularly 5 to 20 parts by weight, per 100 parts by weight of the plastic material as described above. In particular, a solid flame retardant for plastics may be added to the plastic material in the form of a powder or granules. For example, the plastic material can be heated above its melting point with the powder or granule of the flame retardant added, or the molten plastic material can be melt-kneaded with the flame retardant added, and then a plastic molded body of the desired shape can be formed by general methods such as press molding, extrusion molding, injection molding, and blow molding.

[0020] The flame retardant for plastics of the present invention has been described above, but other additives such as colorants, antioxidants, antistatic agents, lubricants, talc, etc., can be added to the flame retardant for plastics of the present invention in the usual manner.

[0021] The present invention will be described in more detail based on the following specific examples, but the present invention is not limited to the following examples.

[0022] (Examples 1-3, Comparative Examples 1-3) Test specimens for the flame retardancy test described later were prepared as follows. 15 parts by weight of polypotassium methacrylate (molecular weight 230,000) was added to 100 parts by weight of each of the base resins: polypropylene (PP, Example 1), polystyrene (PS, Example 2), and polyphenylene oxide (PPO, Example 3). The mixture was kneaded at a temperature above the melting point of the base resin using a mixing roll with a roll diameter of 6 inches and a length of 12 inches. This mixture was formed into a sheet, and the molded sheet was formed into a flat plate of the thickness shown in Table 1 using a hydraulic press at a press pressure of 50 tons. The sheet was then cut into 150 mm x 150 mm pieces to serve as test specimens for the flame retardancy test. For comparison, polypropylene (PP), polystyrene (PS), and polyphenylene oxide (PPO) base resins were molded into flat plates of the thickness shown in Table 1 without the addition of polypotassium methacrylate, and cut into 150 mm x 150 mm pieces to be used as test specimens for flame retardancy testing (Comparative Examples 1-3).

[0023] (Flame Retardancy Test) The flame retardancy test was conducted according to UL94HB, one of the UL94 standards shown below. Specifically, the test specimen was held horizontally, one end was exposed to a flame for 30 seconds, and the burning time and burning distance after the flame was removed were measured, and the burning rate was determined based on these measurements. The results, along with the thickness of the test specimen, burning time, and burning distance, are shown in Table 1.

[0024]

[0025] As is clear from Table 1, the test specimens of each example showed a burning rate that was 10% or more slower than the test specimens of the corresponding comparative examples, indicating that polypropylene (PP), polystyrene (PS), and polyphenylene oxide (PPO) can be suitably made flame-retardant by incorporating the flame retardant for plastics of the present invention.

Claims

1. A flame retardant for plastics comprising a thermally depolymerizable polymer having a structure to which water-soluble functional groups are attached, an alkali metal salt thereof, or an alkaline earth metal salt thereof.

2. The flame retardant for plastics according to claim 1, wherein the thermally depolymerizable polymer having the water-soluble functional group has a structure represented by the following chemical formula. (In the formula, X is hydrogen (H) or an alkyl group having 1 to 3 carbon atoms, and Y is COOH, SO ３ H, OCOOH, OSO ３ H, COO(CH2) ｍ COOH, COO(CH2) ｍ SO ３ H, benzene ring-COOH or benzene ring-SO ３ H, n is a positive integer of 5 to 27,000, and m is a positive integer of 1 to 5.) 3. The flame retardant for plastics according to claim 1, wherein the alkali metal salt is a K salt or a Na salt.

4. The flame retardant for plastics according to claim 1, wherein the alkaline earth metal salt is a Ca salt or a Mg salt.

5. The flame retardant for plastics according to any one of claims 1 to 4, wherein the thermally depolymerizable polymer having the water-soluble functional group is poly(methacrylic acid).

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