JP2000053794A - Flame retardant thermoplastic polyester-based resin foamed material and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject resin foamed material being a flame retardant and gentle to an environment, and blowing well by blowing a composition obtained by adding a specific aromatic phosphorus compound to a thermoplastic polyester-based resin. SOLUTION: This flame retardant thermoplastic polyester-based resin foamed material is obtained by preferably charging a composition obtained by adding 0.5-10 pt.wt. aromatic phosphorus compound of formula I [A, B, D and E are each an aromatic group of formula II (R1 to R5 are each H or a lower alkyl)] to 100 pts.wt. thermoplastic polyester-based resin into an extruder, melting and mixing them, compressing a blowing agent therein, and then extruding the molten mixture to a low pressure zone for blowing. The shape of the foamed material is preferably a particle state. The foamed material is preferably obtained by cutting the foamed material after its extrusion blowing to make foamed particles, putting them into a mold capable of closing the foamed particles but not hermetically closing them, and heating for foaming and melt adhering together. A rheological property-improving agent can be added to the foamed material as necessary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a flame-retardant thermoplastic polyester resin foam and a method for producing the same.

[0002]

2. Description of the Related Art Polyester resins include thermoplastic resins and thermosetting resins. Thermosetting polyester resins are often used together with glass fibers as reinforced plastics, and are rarely used alone. Therefore, the thermosetting polyester resin is not used as a foam. On the other hand, the thermoplastic polyester resin is often used alone or in a state where another resin is laminated on the resin. Therefore, the thermoplastic polyester resin is used as a foam by foaming the same.

[0003] A thermoplastic polyester resin to be a foam is obtained by mixing an aromatic dicarboxylic acid and a dihydric alcohol, that is, a diol, and performing an esterification reaction therebetween to obtain a high-molecular-weight chain. Polyester.
Phthalic acid was frequently used as the carboxylic acid, and ethylene glycol was often used as the diol. A typical example of this type of resin is polyethylene terephthalate. Hereinafter, such a thermoplastic polyester resin is abbreviated as PAT.

[0004] PAT is harmless, colorless and transparent, has excellent mechanical strength such as tensile strength and impact resistance, and has good heat resistance and weather resistance. Therefore, PAT can be used for food containers, industrial members, electric and electronic parts. Widely used to make. Among them, those used as electric and electronic parts have been required to be flame-retardant for safety. As a standard for flame retardancy at that time, a plastic material combustion test specified in UL standard was used, and it was required that the flame resistance be 94 HB or more. This flame retardancy was also required for PAT foams.

[0005] As a method for making PAT flame-retardant, a method described in JP-A-4-142363 is known. This method proposes to mix a brominated aromatic compound and an organotin compound as a flame retardant in PAT. Although the composition obtained in this way is flame retardant, it does not necessarily have the flame retardancy of 94 HB or more in the above-mentioned UL standard, and cannot satisfy the requirement of being more environmentally friendly. . Here, “friendly to the environment” means that unlike a bromine compound or an organotin compound, it does not adversely affect the survival of living organisms.

[0006]

SUMMARY OF THE INVENTION The present invention has been made as a result of intensive studies to satisfy the above-mentioned requirements. In other words, the present invention is to provide a flame-retardant PAT foam which has a flame retardancy of 94 HB or more in the above-mentioned UL standard flame retardancy test, and is environmentally friendly and well foamed. It is assumed that. Another object is to provide a method for producing such a foam.

[0007]

SUMMARY OF THE INVENTION The present inventor has sought to produce a flame-retardant PAT foam by mixing a PAT with a flame retardant containing no halogen element and extruding and foaming the mixture. For that purpose, PAT was foamed using various organic compounds as a flame retardant, and the flame retardancy of the obtained foam was examined. As a result, a specific aromatic phosphate ester was converted to PAT.
It has been found that a PAT foam having a flame retardancy of 94 HB or more according to UL standard can be obtained when mixed. The present invention has been completed based on such knowledge.

Here, the specific aromatic phosphate is
It is a compound having a skeleton of 1,4-bis (phosphate) benzene, and is a compound represented by Chemical Formula 1. here,
A, B, D and E are the same or different aromatic groups, and are aromatic groups represented by Chemical Formula 2. In Formula 2, R ₁ , R ₂ , R ₃ , R ₄ and R
₅ represents hydrogen or a lower alkyl group. Here, the lower alkyl group means a linear or branched alkyl group having 1 to 5 carbon atoms.

The present invention provides a flame-retardant composition obtained by foaming a composition obtained by adding 0.5 to 10 parts by weight of an aromatic phosphorus compound represented by the above chemical formula 1 to 100 parts by weight of a PAT. A PAT foam is provided.

[0010] The present invention also provides a method for producing the above-mentioned flame-retardant PAT foam. The method comprises producing an aromatic phosphorus compound represented by the above chemical formula 1 in 100 parts by weight of PAT. The mixture obtained by adding 0.5 to 10 parts by weight is put into an extruder, melt-mixed, and at the same time, a foaming agent is press-fitted into the extruder, extruded into a low-pressure region and foamed to form a foam. is there.

Here, A, B, D and E in the chemical formula 1
Represents an aromatic group represented by Chemical Formula 2 as described above. A, B, D and E may be the same as each other or may be different.

Among the compounds belonging to the above formula 1,
A, B, D and E are all the same, and furthermore, they are aromatic groups represented by the chemical formula 2, wherein R ₃ , R ₄ and R ₅ are hydrogen, and R ₁ and R ₂ are all methyl groups. Is preferred for use in the present invention.
One. This compound specifically has the following structural formula.

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According to the present invention, the compound represented by the chemical formula 1 and PAT are used in an amount of 0.5 to 0.5 parts by weight of the former to 100 parts by weight of the latter.
It is characterized in that the composition mixed at a ratio of 10 parts by weight is foamed. In that ratio, the former is preferably 1 to 2 parts by weight. What was mixed in that proportion,
The compound of Formula 1 and PAT are well compatible to form a uniform composition. The PAT composition thus obtained is flame retardant, and has a flame retardancy of 94 HB or more in a UL standard flame retardancy test. In addition, this composition has relatively good thermal stability, and does not decompose even when it is placed in an extruder and heated to around the melting temperature of PAT. In addition, the composition is suitable for extrusion foaming, since the foaming agent commonly used for foaming PAT, when pressed into the extruder, absorbs smoothly.

The compound represented by Chemical Formula 1 (hereinafter referred to as a phosphorus compound) is generally solid, has a melting point of 70 ° C. or more, and is relatively stable to heat. Since a phosphorus compound contains as many as five aromatic groups in one molecule, it is well compatible with PAT containing phthalic acid as a component and containing an aromatic group. For this reason, even if 10 parts by weight of the phosphorus compound is added to 100 parts by weight of the PAT, the phosphorus compound is well compatible with the PAT and forms a homogeneous composition. This composition has high flame retardancy.

The PAT used in the present invention is a high-molecular chain polyester obtained by reacting an aromatic dicarboxylic acid with a dihydric alcohol as described above.
Of these, terephthalic acid is most frequently used as the dicarboxylic acid, but isophthalic acid, 2,6-naphthalenedicarboxylic acid, and the like are also used as a mixture with terephthalic acid. In addition, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, and diphenoxy dicarboxylic acid are also used as dicarboxylic acids.

On the other hand, aliphatic alcohols are often used as dihydric alcohols constituting PAT, but phenols are also used, and alcohols containing an aliphatic ring are also used. As the aliphatic dihydric alcohol, ethylene glycol is often used, and trimethylene glycol, tetramethylene glycol, neopentylene glycol, and hexamethylene glycol are used. Phenols include catechol, resorcinol,
Hydroquinone, orcin and the like can be used. As the alcohol containing an aliphatic ring, p-dimethoxycyclohexane can be used.

Among the above-mentioned PATs, the one suitable for use in the present invention is polyethylene terephthalate made by condensing ethylene glycol and terephthalic acid, and it is also possible to condense butylene glycol with terephthalic acid. Polybutylene terephthalate made from
-Polycyclohexane terephthalate produced by condensing dimethoxycyclohexane and terephthalic acid. Such PATs are commercially available. In the present invention, these commercially available PATs can be used alone or as a mixture. PAT can also be used by mixing a small amount of other resin with it.

In the present invention, a composition is prepared by adding a phosphorus compound to make PAT flame-retardant. In this case, the amount of the phosphorus compound added is 0.5 to 10 parts by weight based on 100 parts by weight of the PAT. In order to make the mixture thus obtained into a composition, it is preferable that the mixture is put into an extruder and melt-kneaded. Because, when using an extruder, the mixture is melt-kneaded in it, and at the same time, the blowing agent is pressed into this,
This is because a foam can be formed at once.

In the present invention, in addition to the PAT and the phosphorus compound,
If necessary, a viscoelasticity improver is further added to this. It is because PAT has low melt viscosity or melt tension,
Since it is difficult to extrude and foam, it is added for the purpose of increasing the melt viscosity of PAT. Preferred viscoelasticity improvers are acid dianhydrides such as pyromellitic anhydride, metal compounds of groups 1, 2 or 3 of the periodic table, polyfunctional epoxy compounds, oxazoline compounds and oxazine compounds. Among these, it is preferable to use an acid dianhydride and a metal compound of the first, second or third group.

In practicing the present invention, various auxiliaries can be further added, if necessary, in addition to those described above. For example, a bubble regulator such as talc powder,
Nucleating agents such as sodium carbonate, antioxidants, heat stabilizers, ultraviolet absorbers, lubricants, release agents, dyes, pigments, antistatic agents,
Fillers and the like can be added.

In general, PAT has a property of being easily hydrolyzed at high temperatures. Therefore, in the present invention, it is preferable to melt-knead the PAT after reducing the water content of the PAT as much as possible. The water content is 200 ppm or less,
It is preferable that the content is not more than 00 ppm. for that purpose,
The PAT is put into a dehumidifying dryer and brought to a temperature of 80 to 180 ° C., and dried air having a dew point of −20 ° C. or less is added to the PAT.
It is preferable to dry for more than an hour or dry in a microwave dryer at a temperature of 80 to 180 ° C. for 1 hour or more.

In order to melt-mix the above-mentioned mixture and to add a foaming agent thereto to form a foam, it is preferable to extrude and foam the mixture as described above. Extrusion foaming means that the above-mentioned mixture is placed in an extruder, the mixture is heated and melted in the extruder, kneaded to a uniform composition, and a foaming agent is pressed in from the middle of the extruder to form a foamable composition. In this method, the foamable composition is extruded from an orifice of a die provided at the tip of an extruder into a low-pressure region, and foamed to obtain a foamed molded product.

As the foaming agent, various foaming agents which have been used for foaming PAT can be used. For example, propane, n-butane, i-butane, n
-Saturated aliphatic hydrocarbons such as pentane, i-pentane, saturated alicyclic hydrocarbons such as cyclohexane, halogenated hydrocarbons such as methyl chloride, ethers such as dimethyl ether; An active gas can be used.

In the case of extrusion foaming, various shapes of PAT foam can be produced by changing the orifice shape of a die provided at the tip of the extruder. For example, the orifice can be made straight to make a plate-like or sheet-like foam, and the orifice can be made annular to make a cylindrical molded body. Also, a cut extending in the extrusion direction can be made in the obtained cylindrical molded body, and the cut can be opened to form a flat sheet. Further, the flat foamed sheet is cut into particles. Can also. In addition, it is also possible to use a die provided with one small hole or a large number of small holes, extrude the foamable PAT from the small holes to form a string-like foam, and cut it into particles. Alternatively, the foam may be cut into particles at almost the same time as the foamable PAT is extruded from the small holes and foamed. The expanded particles thus obtained are:
By the foam molding method described below, it is possible to foam-mold another foam molded article.

The above-mentioned expanded particles have the property of expanding when heated again. Also, when the above-mentioned expanded particles are heated and expanded in a mold that can be closed but cannot be sealed, similarly to the pre-expanded particles of polystyrene, the particles fuse with each other to form a mold cavity. It has the property of being a foam. In addition, the above-mentioned foamed particles were put in a sealed container in advance, carbon dioxide gas, nitrogen, after pressurizing an inert gas such as helium, and then press-fitted until immediately before use in secondary foaming molding in a mold. If it is kept in a gas atmosphere, it will have a greater foaming ability when it is put into a mold and subjected to secondary foam molding. Thus, the particles described above can be placed in a mold that can be closed but not sealed, and heated and foamed to produce a foam molded article that conforms to the mold cavity. Since the obtained foam molded article has a shape corresponding to the mold cavity, it is possible to obtain various desired shapes and sizes by changing the mold cavity. Here, a mold that can be closed but cannot be sealed is a mold that has a small through hole in the mold cavity wall surface that does not allow softened resin to pass through but passes steam for heating or gas derived from a foaming agent. That is.

According to the present invention, by adjusting the crystallinity of the thus obtained PAT foam, the PAT
The amount of heat absorbed by the foam is increased to delay the combustion time, thereby improving the flame retardancy. More specifically, since PAT is a crystalline resin, it shows heat of crystallization and heat of crystallization. Therefore, by setting the value of (heat of crystallization-heat of crystallization) to 21 mj / mg or more, PAT Occasionally, the PAT foam absorbs heat, so that the burning time can be reduced. A more preferable value of (heat of crystal fusion-heat of crystallization) is 28 mj / mg. The heat of crystal fusion and heat of crystallization of the PAT foam were measured by a differential scanning calorimeter (DS).
It can be easily measured by C).

[0027]

According to the present invention, a phosphorus compound represented by the chemical formula 1 is used as a flame retardant, and the amount of the phosphorus compound is reduced to PAT10.
Since the amount is 0.5 to 10 parts by weight based on 0 part by weight, a uniform composition can be produced. The composition exhibits sufficient flame retardancy and promotes the action of the blowing agents that have been used to foam PAT. Therefore, a flame-retardant PAT foam can be easily obtained by using this composition. On top of that, the P
AT foam is environmentally friendly and has no difficulties in disposal.

As a method for producing a PAT foam, the above-mentioned composition is prepared by using a conventional extruder as it is and extruding the PA by an extrusion foaming method.
This is advantageous because the T-foam can be manufactured at once. Further, by making the shape of the foam thus obtained into particles, the particles are placed in a mold that can be closed but cannot be sealed, and heated and foamed to have the shape of the mold cavity. Flame-retardant foamed molded article. The present invention provides such benefits.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The advantages and advantages of the present invention will be specifically described below with reference to Examples and Comparative Examples. In the following, simply “parts” means parts by weight.

[0030]

Example 1 100 parts of a polyethylene terephthalate resin having an IV value of 1.07 (SA-1206 manufactured by Unitika) was added to a phosphorus compound represented by the chemical formula 3 (S-1 manufactured by Daiichi Kogyo Seiyaku).
X-6502) 2 parts, 1 part of talc, 0.15 part of pyromellitic anhydride, and 0.01 part of sodium carbonate were added to form a mixture, and this mixture was charged into a single-screw extruder having a diameter of 65 mmφ. .

The cylinder temperature of the extruder is set to 270 to 285.
The mixture was melted and kneaded while maintaining the temperature at ° C. From the middle of the cylinder, butane (foaming agent) is press-fitted at a ratio of 0.4 parts,
A foamable melt was made. This melt was extruded into the atmosphere from a circular die having a diameter of 80 mmφ, foamed, and taken out at a cooled end. On the way, the extrudate
The sheet was advanced along a cylindrical mandrel of 5 mmφ, the shape was adjusted during that, and a part of the cylindrical body was cut out at that point to form a sheet, thus obtaining a flat sheet.

The obtained foamed sheet has a thickness of 1.2 mm,
The grammage was 600 g / m ² . 250 from this sheet
A sample having a size of × 250 mm was cut out, sandwiched between two upper and lower heating plates having a surface temperature of 180 ° C., and pre-heated by press-contacting for 6 seconds. The degree of crystallinity was adjusted to obtain a flat foam plate. This foam board has a thickness of 1.6 mm and a value of (heat of crystal fusion-heat of crystallization) of 32.2 mj / m.
g, and the burning time at 94HB of UL standard was excellent in that the flame disappeared before the arrival of the 3-inch mark.

[0033]

Example 2 A foamed sheet and a flat foamed board were obtained in the same manner as in Example 1 except that the amount of the phosphorus compound represented by Chemical Formula 3 was changed to 1.2 parts. The obtained flat foam plate has a thickness of 1.6 mm, a value of (heat of crystal fusion-heat of crystallization) of 28.2 mj / mg, and a burning time of 94 inches in UL standard of 3 inches. It had excellent flame retardancy, so that it all disappeared before the line arrived.

[0034]

Example 3 100 parts by weight of recovered pellets of a PET bottle (manufactured by Yonoh Pet Recycle Co., Ltd.), 4 parts of a phosphorus compound represented by Chemical Formula 3 (SX-6502 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 0.31 part by weight of pyromellitic dianhydride and 0.03 part by weight of sodium carbonate as a modifier are supplied to an extruder (diameter: 65 mm, L / D ratio: 35), and the number of rotations of the screw is increased. 50 rpm, barrel temperature 270
While melting and mixing at 条件 290 ° C., butane as a blowing agent was injected at a rate of 1.1% by weight to the mixture from a press-fitting tube connected in the middle of the barrel. A multi-nozzle mold in which the molten mixture is connected to the end of a barrel (15 small holes with a diameter of 0.8 mm are arranged)
After being extruded and foamed from each small hole, it was immediately cooled in a cooling water tank.

Then, the cooled cord-like foam was sufficiently drained, and cut into small particles using a pelletizer to obtain foamed particles. The bulk density of the obtained expanded particles was 0.14 g / cm ³ , and the particle size was 1.5 to 2.4 mm. The obtained foamed particles were placed in a closed container, carbon dioxide gas was injected under a pressure of 0.49 MPa, and then kept for 4 hours.

Next, 336 g of the foamed particles taken out of the closed container were immediately weighed to an inner dimension of 300 mm × 400 mm.
After filling into a mold of × 20 mm that can be closed but cannot be sealed and clamped, a gauge pressure of 0.02 MPa
Steam for 10 seconds, then gauge pressure 0.06MPa
Was introduced for 20 seconds, and the expanded particles were heated and expanded, and simultaneously fused. Further, the foam was kept as it was for 120 seconds and then cooled with water to obtain a polyester resin foam. In this way, a rectangular parallelepiped foam molded article having the same outer dimensions of 300 mm × 400 mm × 20 mm as the inner dimensions of the mold was obtained. The density of the obtained molded body was 0.14 g / cm ³ , the value of (heat of crystal fusion-heat of crystallization) was 38.5 mj / mg, and the burning time in UL standard 94HB was 3 inches. It had excellent flame retardancy, so that it all disappeared before the line arrived.

[0037]

Comparative Example 1 In place of the phosphorus compound represented by Chemical Formula 3 in Example 1, TXP (Trixylenyl phosphate) manufactured by Daihachi Chemical Co., Ltd. (melting point: -15 ° C., phosphorus content: 7.6%)
An attempt was made to produce a foamed sheet in exactly the same manner as in Example 1, except that 2.5 parts were pressed in from the middle of the extruder, but a foamed sheet could not be produced stably.
Therefore, the obtained foamed sheet had a poor surface condition.

[0038]

Comparative Example 2 A foam sheet was produced in exactly the same manner as in Example 2, except that 0.1 part of the compound represented by the chemical formula 3 was used as the phosphorus compound. The obtained foamed sheet had a thickness of 1.6 mm and a value of (heat of crystal fusion-heat of crystallization) of 7.5 mj / mg. This foamed sheet had a burning time of 55 seconds in 94HB of UL standard, and was not considered to have sufficient flame retardancy.

[0039]

Comparative Example 3 Except that no phosphorus compound was used at all, foamed particles were prepared in the same manner as in Example 3, and then put in a mold and heated and fused to form a rectangular parallelepiped foam molded article. made. The external dimensions of the obtained molded body are 300 × 4
Although it was 00 × 20 mm and conformed to the mold cavity, the value of (heat of crystal fusion−heat of crystallization) was 36.9 mj / mg. When the flame retardancy of this molded article was measured based on the UL standard, it continued to burn until the molded article disappeared, and was not considered to be flame retardant.

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Claims (5)

[Claims] 1. To 100 parts by weight of a thermoplastic polyester resin, A flame-retardant thermoplastic polyester resin foam, characterized by foaming a composition to which 0.5 to 10 parts by weight of an aromatic phosphorus compound represented by the formula (1) is added. Here, A, B, D and E are: Wherein R ₁ , R ₂ , R ₃ , R ₄ and R ₅ all represent hydrogen or a lower alkyl group. 2. The aromatic phosphorus compound is the same as A, B, D and E in the above chemical formula, and R
_3, R ₄ and R ₅ are hydrogen, R ₁ and R ₂ is characterized in that it is a methyl group, a thermoplastic polyester resin foam flame retardant of claim 1. 3. The flame-retardant thermoplastic polyester resin foam according to claim 1, wherein the foam has a particle shape. 4. An aromatic phosphorus compound represented by the chemical formula 1 in an amount of 0.5 to 1 based on 100 parts by weight of a thermoplastic polyester resin.
The mixture obtained by adding 0 parts by weight to an extruder is melt-mixed, a foaming agent is press-fitted into the extruder, and then extruded into a low-pressure region to form a foam. How to make the body. here,
A, B, D and E represent the same as described in claim 1. 5. An aromatic phosphorus compound represented by the formula (1) in an amount of 0.5 to 1 based on 100 parts by weight of a thermoplastic polyester resin.
The mixture obtained by adding 0 parts by weight was put into an extruder, melt-blended and a foaming agent was pressed into the mixture, and then extruded into a low-pressure region to foam, and then the obtained foam was cut into foamed particles, A method for producing a flame-retardant thermoplastic polyester resin foam, characterized in that the foamed particles are placed in a mold that can be closed but cannot be sealed, heated, foamed and fused. Here, A, B, D and E represent the same as described in claim 1.