JPH1060192A - Flame retardant resin composition and sheet made therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin composition made flame retardant without detriment to the flexibility of the constituent ethylene/vinyl acetate copolymer resin and can give sheets having improved processability by mixing the ethylene/vinyl acetate copolymer resin with a polyethylene so as to form a composition having a specified MFR. SOLUTION: This composition comprises 100 pts.wt. ethylene/vinyl acetate copolymer resin and 5-70 pts.wt. polyethylene and has an MFR of 3 or below. Polyethylene is a resin having a burning rate lower than that of an ethylene/ vinyl acetate copolymer resin and is a flexible resin not detrimental to the flexibility of the ethylene/vinyl acetate copolymer resin. The MFR of the composition is limited to 3 or below by reason that this can assure its extrudability into sheets and their good processability. It is also possible to add 1-20 pts.wt. inorganic filler to the composition in order to further retard its burning rate. When the inorganic filler is used in a small amount, it is effective to prevent the sheet from sagging when softened by heating and to accelerate the cooling of the sheet rather than to retard its burning rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a composition of ethylene-vinyl acetate copolymer resin and a sheet thereof. This sheet is suitable for automotive parts as a rubber product replacement.

[0002]

2. Description of the Related Art Sheets of ethylene vinyl acetate copolymer resin are flexible and inexpensive, so they are used for secondary processing such as vacuum molding, and are used as substitutes for rubber products in the fields of electric products and automobile parts. Widely used. Since ethylene-vinyl acetate copolymer resin is flammable, it is well known to add a flame retardant to make it difficult to burn. However, in order to make it difficult to burn, it is necessary to add a large amount of a flame retardant. When a large amount of a flame retardant is added to the ethylene-vinyl acetate copolymer resin, the tension at the time of melting is reduced and the stretchability is impaired, so that it is difficult to perform the operation of manufacturing a sheet by extrusion. In addition, the addition of a large amount of a flame retardant causes loss of original flexibility and impaired expandability, making it difficult to perform vacuum forming and pressure forming.

[0003]

SUMMARY OF THE INVENTION It is difficult to make an inherently flammable ethylene-vinyl acetate copolymer resin difficult to burn (to make it flame-retardant). Therefore, a problem to be solved by the present invention is to reduce the burning speed (make it slow burning) when it burns. An ethylene vinyl acetate copolymer resin composition and a sheet thereof are provided. The sheet also has flexibility and good secondary formability such as good vacuum formability.

[0004]

The present invention solves the above-mentioned problems by providing a resin composition in which polyethylene is blended with an ethylene-vinyl acetate copolymer resin. Polyethylene is a resin having a lower burning rate than the ethylene-vinyl acetate copolymer resin, and is a soft resin that does not impair the flexibility of the ethylene-vinyl acetate copolymer resin. Polyethylene needs to be blended in a range that does not impair the flexibility and does not impair the burning rate. The polyethylene is used in an amount of 5 to 70 parts by weight based on 100 parts by weight of the ethylene-vinyl acetate copolymer resin. Further, the MFR as the resin composition is set to 3 or less for the purpose of ensuring extrudability into a sheet and good secondary moldability. By the blending of polyethylene, the melt viscosity at the time of extrusion molding into a sheet or at the time of vacuum molding as secondary processing is increased. The sagging when the sheet is heated and softened is suppressed, and the vacuum formability is also improved. The measurement of MFR is based on JIS K7210
MFR is 3 and 10
It indicates that the extrusion amount per minute is 3 g.

In order to further reduce the burning speed,
For 100 parts by weight of ethylene vinyl acetate copolymer resin,
5 to 70 parts by weight of polyethylene and 1 to 20 parts by weight of an inorganic filler can be blended so as not to impair flexibility. The MFR of the resin composition is similarly set to 3 or less.
In the case where a small amount of the inorganic filler is blended, the effect of suppressing the sagging of the sheet during heating and softening and promoting the cooling of the sheet is more effective than the effect of reducing the burning rate. In order to further reduce the burning rate by another means, the ethylene-vinyl acetate copolymer resin 1
With respect to 00 parts by weight, 5-70 parts by weight of polyethylene,
2 to 20 parts by weight of a halogen-based flame retardant can be blended so as not to impair flexibility. MF as resin composition
R is similarly set to 3 or less.

[0006] The thickness of the sheet made of each of the flame retardant resin compositions is 1 mm or more. This is because, if the thickness of the sheet is small, even if the above-described flame retardant resin composition is used, a remarkable effect of reducing the burning rate is not exhibited.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The composition of the ethylene-vinyl acetate copolymer resin according to the present invention needs to have an MFR of 3 or less, but preferably has an MFR of 2 or less. Further, the vinyl acetate content in the composition of the ethylene-vinyl acetate copolymer resin is preferably 10% by weight or less, and more preferably the vinyl acetate content is 5% by weight or less. still,
When the vinyl acetate content is less than 3% by weight, the composition is usually not regarded as an ethylene-vinyl acetate copolymer resin composition.
When a sheet made of a resin composition in which polyethylene is blended with an ethylene-vinyl acetate copolymer resin is produced by extrusion molding, the difference between the melting temperatures of the ethylene-vinyl acetate copolymer resin and polyethylene is set to 40 ° C. or less. If the difference between the melting temperatures is too large, an unmelted product is formed at the time of extrusion, so that the appearance of the sheet deteriorates. In addition, it is not preferable because the appearance of the product is deteriorated by the vacuum forming of the secondary processing. As the resin to be mixed with the ethylene-vinyl acetate copolymer resin, a polyolefin-based thermoplastic elastomer, a polystyrene-based thermoplastic elastomer, or the like can be used in addition to polyethylene, and two or more of these can be used in combination.

[0008] As an inorganic filler compounded in the resin composition,
Talc, mica, silica, antimony oxide, magnesium hydroxide, aluminum hydroxide, barium metaborate,
Zinc borate, phosphate, and the like can be employed, but are not limited thereto. It is also possible to use two or more inorganic fillers in combination. If the amount of the inorganic filler exceeds 20 parts by weight based on 100 parts by weight of the polyethylene vinyl acetate copolymer resin, the moldability is impaired in addition to the flexibility. As the halogen-based flame retardant to be mixed with the resin composition, any of a bromine-based and a chlorine-based flame retardant can be adopted. In order to expect the effect of the addition of the flame retardant, it is necessary to add 2 parts by weight or more of the flame retardant to 100 parts by weight of the ethylene-vinyl acetate copolymer resin. It is preferably at least 5 parts by weight.

[0009]

【Example】

Examples 1 to 3, Conventional Example 1 Ethylene vinyl acetate copolymer resin (EVA) having a vinyl acetate content of 8% by weight, MFR of 1.5, low density polyethylene (LDPE) of MFR 0.3, and high density polyethylene of MFR 0.3 ( HDPE) was mixed with the composition (parts by weight) shown in Table 1, and the vinyl acetate content and MFR as shown in Table 1 were mixed.
Was prepared. This was molded with a single screw extruder to obtain a 1.2 mm thick sheet.

[0010]

[Table 1]

Each of the extruded sheets was subjected to a combustion test based on MVSS 302 (combustibility standards for automotive interior materials). Further, as an evaluation of the flexibility, the Shore hardness specified in JIS was measured. Furthermore, as an evaluation of the vacuum formability of the secondary processing, the presence or absence of the die attached to the sheet during vacuum forming was observed, and the gloss and gloss after vacuum forming were measured. Table 2 shows the results. The MVSS 302 holds the sheet in a horizontal state, ignites the sheet by bringing a fire close to the edge of the sheet for 15 seconds, and measures the burning rate. Specifically, it measures the speed of burning by 250 mm after burning 38 mm from the edge, and is classified as follows according to the burning speed. Self-extinguishing (flame-retardant): self-extinguishing by burning 5 cm or less within 60 seconds of ignition. Slow flammability 1st class: Burning speed 50 mm / min or less. Grade 3: Burning speed of 75 to 100 mm / min or less The gloss and gloss were measured by a gloss meter.

[0012]

[Table 2]

From Table 2, it can be seen that the sheet according to the embodiment can reduce the burning rate without greatly impairing the flexibility of the conventional example 1. Further, it can be seen that the adhesion of the sheet to the mold during the vacuum forming is eliminated, and the gloss and gloss after the vacuum forming are suppressed to the same level as or less than conventionally.

Examples 4 to 7, Conventional Example 2 Ethylene vinyl acetate copolymer resin (EVA) having a vinyl acetate content of 3.5% by weight, MFR of 1.5, high density polyethylene (HDPE) of MFR of 0.3, and inorganic filler (Example 6:
Magnesium hydroxide, Example 7: phosphate) was mixed in the composition (parts by weight) shown in Table 3 to prepare a resin composition having a vinyl acetate content and an MFR as shown in Table 3. This was molded with a single screw extruder to obtain a 1.3 mm thick sheet. Table 4 shows the results of evaluation of flammability, flexibility, and vacuum formability as described above.

[0015]

[Table 3]

[0016]

[Table 4]

From Table 4, it can be seen that the sheet according to the example can reduce the burning rate with the same flexibility as the conventional example 2. Further, it can be seen that the sheet does not adhere to the mold during the vacuum forming, and the gloss and gloss after the vacuum forming are suppressed to the same level as or less than the conventional one. Even if a small amount of an inorganic filler is added, the flexibility is not impaired, which is good.

Examples 8 to 10, Comparative Example 1, Conventional Examples 3 to 4 Ethylene vinyl acetate copolymer resin (EVA) having a vinyl acetate content of 5% by weight, MFR 2 or 3, and low density polyethylene (LDPE) having an MFR of 0.3 Were mixed in the composition (parts by weight) shown in Table 5 to prepare a resin composition having a vinyl acetate content and an MFR as shown in Table 5 (EV of Example 8).
A is MFR3, EVA of Examples 9 and 10 is MFR2).
This was molded with a single screw extruder to obtain a 1.2 mm thick sheet. In Comparative Example 1, a resin composition having a high vinyl acetate content was examined using an ethylene-vinyl acetate copolymer resin having a high vinyl acetate content (vinyl acetate content: 10% by weight, MFR: 9). Things. Table 6 shows the results of evaluation of flammability, flexibility, and vacuum formability as described above.

[0019]

[Table 5]

[0020]

[Table 6]

From Table 6, it can be seen that the sheets according to the examples can reduce the burning rate without significantly impairing the flexibility of Comparative Example 1, Conventional Examples 3 and 4. Further, it can be seen that the sheet does not adhere to the mold during the vacuum forming, and the gloss and gloss after the vacuum forming are suppressed to the same level as or less than the conventional one. Even if polyethylene is blended, if the MFR of the ethylene-vinyl acetate copolymer resin composition is large as in Comparative Example 1, the effect of blending polyethylene (slow flame retardancy) is not exhibited. When the MFR is 3 or less as in the eighth and ninth embodiments, the effect of the slow-flammability is exhibited.

Examples 11 to 12 Ethylene vinyl acetate copolymer resin (EVA) having a vinyl acetate content of 3.5% by weight, MFR of 1.5, high density polyethylene (HDPE) of MFR 0.3 and trioxide as a flame retardant auxiliary A bromine-based flame retardant combined with antimony was mixed in the composition (parts by weight) shown in Table 7 to prepare a resin composition having a vinyl acetate content and an MFR as shown in Table 7. This was molded with a single screw extruder to obtain a 1.3 mm thick sheet. Table 8 shows the results of evaluating the flammability, flexibility, and vacuum formability in the same manner as described above. It should be noted that addition of a small amount of the phosphorus-based flame retardant did not have the effect of making it difficult to burn.

[0023]

[Table 7]

[0024]

[Table 8]

From Table 8, it can be seen that the sheet according to the example can reduce the burning rate with the same flexibility as the conventional example 2. Further, it can be seen that the sheet does not adhere to the mold during the vacuum forming, and the gloss and gloss after the vacuum forming are suppressed to the same level as or less than the conventional one. Even if a small amount of a halogen-based flame retardant is added, the flexibility is not impaired, and is good.

[0026]

As described above, the sheet containing the ethylene-vinyl acetate copolymer resin according to the present invention as a main component can be used without any loss in flexibility of the ethylene-vinyl acetate copolymer resin when ignited. Burning speed is slow (slow flammability). Further, even after secondary processing such as vacuum formability, gloss and luster are hardly produced, and it is suitable for fields such as automobile parts.

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Claims (4)

[Claims] (1) Ethylene vinyl acetate copolymer resin 10
0 part by weight (2) 5 to 70 parts by weight of polyethylene, having an MFR of 3 or less. (1) Ethylene vinyl acetate copolymer resin 10
0 part by weight (2) 5 to 70 parts by weight of polyethylene (3) 1 to 20 parts by weight of an inorganic filler, wherein the MFR is 3 or less. 3. An ethylene-vinyl acetate copolymer resin 10.
0 part by weight (2) 5 to 70 parts by weight of polyethylene (3) 2 to 20 parts by weight of a halogen-based flame retardant, wherein the MFR is 3 or less. 4. A flame retardant resin sheet comprising the flame retardant resin composition according to claim 1 and having a thickness of 1 mm or more.