JP5698575B2 - Flame retardant resin composition - Google Patents

Description

  The present invention relates to a flame retardant resin composition that has excellent flame retardancy and does not generate halogen gas during combustion. Specifically, the present invention has a high expansion start temperature and expansion at 1000 ° C. A flame-retardant resin composition containing high-expansion graphite (hereinafter also referred to as “TEG” as an abbreviation for Thermally Expandable Graphite) and polybutylene terephthalate (hereinafter also referred to as “PBT” as an abbreviation for Polybuthylene terephthalate). Related to things.

  Polybutylene terephthalate (PBT) is a crystalline thermoplastic resin obtained by direct polycondensation of terephthalic acid and 1,4-butanediol or by polycondensation by transesterification of dimethyl terephthalate and 1,4-butanediol. Excellent mechanical properties, heat resistance, electrical properties, and dimensional stability. PBT is very excellent in moldability compared to polyethylene terephthalate of the same family, so molded products are mainly used, and it is widely used for electrical, electronic parts, parts for vehicles (automobiles, railways), building materials, etc. Yes.

  Here, many of the resin materials used for the above applications are required to be flame retardant. In order to impart flame retardancy to a resin composition having a combustible resin as a main component, a flame retardant is usually contained. PBT is a halogen flame retardant such as bromine, which is currently the most common flame retardant. Because of its familiarity, a flame retardant grade of a resin composition (hereinafter referred to as “PBT resin composition”) containing PBT as a main resin component (hereinafter referred to as “PBT resin composition”) contains this halogen flame retardant. The flame retardancy is given by this. In the PBT resin composition, “with PBT as the main resin component” means that the content of PBT is so large that the thermal behavior during preparation and molding of the resin composition is dominated by PBT. The content range is influenced by the type of other components (particularly the resin) to be added and is not clearly defined, but 80% by mass or more in the total resin content of the resin composition will be one standard.

In order to impart flame retardancy to this PBT resin composition, a halogen-based flame retardant generally used is that the halogen gas generated when the resin composition is heated is burned by the resin volatiles and oxygen. In order to exert flame retardancy by suppressing the reaction, an essentially toxic halogen gas is generated during use. Further, in the flame retardant grade of PBT containing a halogen-based flame retardant, the halogen content contained may be a factor for increasing the processing cost at the disposal stage or a limiting factor for the application range at the recycling stage. That is, since it contains a halogen-based flame retardant, the flame retardant grade PBT resin composition has become an environmentally hazardous substance. For this reason, the movement which regulates the use of flame retardant grade PBT resin compositions containing the halogenated flame retardant mainly in Europe where environmental awareness is high is spreading.
Therefore, in a resin composition containing PBT, imparting flame retardancy without using a halogen-based flame retardant has become an important issue in promoting its use.

  By the way, as an alternative to conventional halogen-based flame retardant materials having such environmental problems, a polymer composition containing a polymer and thermally expandable graphite (hereinafter referred to as “TEG-polymer composition”). ) Have been proposed (Patent Documents 1 and 2) and are beginning to be adopted. When this TEG-polymer composition is exposed to a high temperature, the heat-expandable graphite in the TEG-polymer composition expands and covers the surface of the polymer, thereby preventing the TEG-polymer composition from burning. In addition, since this expansion is an endothermic reaction, it is possible to take away ambient heat and calm down the combustion. Moreover, it is possible to draw the polymer component melted by heat into the gap between the graphite crystals generated by thermal expansion. The polymer component drawn into the voids becomes deficient in oxygen and difficult to burn.

The basic characteristics of thermally expandable graphite, which is an excellent flame retardant imparting material, can be evaluated by the degree of expansion and the expansion start temperature.
The degree of expansion is a quantitative indication of the expansion volume when heated to a temperature at which the thermally expandable graphite can sufficiently expand (for example, 1000 ° C.), and cc / g is commonly used. This degree of expansion strongly affects the flame retardancy and other properties of the TEG-polymer composition. For example, when the degree of expansion of the thermally expandable graphite is low, it is necessary to add a large amount of the thermally expandable graphite to the polymer in order to obtain a predetermined flame retardancy. In this case, it becomes difficult to perform sufficient kneading in the preparation stage of the TEG-polymer composition and the like, resulting in a decrease in productivity and a decrease in product quality (a decrease in uniformity in the product).

  The expansion start temperature is a temperature that becomes 1.1 times or more of the original volume when the heat-expandable graphite is heated under certain conditions. Currently, many thermally expandable graphites on the market have an expansion start temperature of around 200 ° C., and therefore the types of polymers that can be applied as TEG-polymer compositions are limited.

  The TEG-polymer composition is often prepared in a heated state using a kneader, and shape processing is often performed in a heated state using a molding machine. The heating temperature in these cases depends on the thermomechanical properties of the polymer. For this reason, when the expansion start temperature is about 200 ° C., depending on the type of polymer (for example, a high-melting-point thermoplastic material), expansion of the heat-expandable graphite is started by heating in material preparation and / or shape processing. That is, some graphite delamination occurs during kneading with the polymer, and the thermal expansibility of the thermally expansible graphite decreases. A polymer composition containing such deteriorated thermally expandable graphite cannot exhibit the original flame retardancy.

Further, since gas is released when the thermally expandable graphite expands, there is a concern that foaming occurs inside the polymer, and operations such as kneading and molding cannot be performed sufficiently.
For the reasons described above, the conventional heat-expandable graphite can be applied only to polyethylene, polypropylene having a melting point of 200 ° C. or less, polyurethane that is liquid at room temperature, etc., and to a resin composition containing a high melting point PBT. Was not applicable.

JP-A-6-73251 JP-A-6-25476

  This invention makes it a subject to provide a flame-retardant PBT resin composition provided with a halogen-free flame-retardant material.

The present invention completed as a result of intensive studies by the present inventors to solve the above-mentioned problems is as follows.
(1) 100 parts by weight of polybutylene terephthalate, 11.0 parts by weight to 30 parts by weight of thermally expandable graphite having an expansion start temperature of 285 ° C. or higher and an expansion degree at 1000 ° C. of 180 cc / g or more, used as a neutralizing agent The alkaline earth metal compound is 0.14 parts by mass or more and 1.2 parts by mass or less in terms of alkaline earth metal, and the phosphate ester is 0.56 parts by mass or more and 5.21 parts by mass or less in terms of phosphorus. A flame-retardant polybutylene terephthalate resin composition characterized by that.

  “Flame retardancy” in the “flame retardant polybutylene terephthalate resin composition” means a property that is determined to be at least V-2 in the UL94 combustion test (1/8 ”). The “composition” has the same meaning as the “PBT resin composition” described above.

  The “expansion start temperature” indicating the characteristics of the thermally expandable graphite refers to the temperature of the thermally expandable graphite increased from 150 ° C. at a rate of 5 ° C. per minute, and the volume is read every 5 ° C. The temperature when expanded by 1 time or more is referred to as “degree of expansion at 1000 ° C.” means the volume (cc) per unit g when the thermally expandable graphite is held at 1000 ° C. for 10 seconds.

(2) The composition according to (1) above, wherein the alkaline earth metal compound contains magnesium and / or calcium.
(3) The composition according to (1), wherein the ratio of the phosphate ester content (unit: parts by mass) to the thermally expandable graphite content (unit: parts by mass) is 0.2 or more and 3.0 or less. .

  The PBT resin composition is used in the PBT resin composition according to the present invention, where heating at about 260 ° C. is required in material preparation (specifically, kneading operation) and shape processing (specifically, molding processing). Since the expansion start temperature of the thermally expandable graphite of TEG is 285 ° C. or higher, the deterioration of the TEG characteristics due to the heat applied during these operations is sufficiently suppressed. In addition, since a TEG having a particularly high expansion rate of 180 cc / g or more at 1000 ° C. is used as a blending raw material, the content of TEG in the PBT resin composition can be reduced. Since TEG is a powder and contributes to lowering the fluidity of the PBT resin composition when kneading or molding, it is possible to reduce the TEG content in the PBT resin composition. This means that the fluidity of the PBT resin composition is increased during processing, and as a result, these operations are facilitated. Moreover, since the heating temperature required in order to ensure the fluidity | liquidity of a PBT resin composition can be lowered | hung, the possibility of deterioration of TEG in the process of material preparation and shape processing can be made still lower.

  Therefore, according to the present invention, it is realized to provide a flame retardant PBT resin composition using a halogen-free flame retardant at an industrial level using TEG.

Hereinafter, the best mode for carrying out the PBT resin composition according to the present invention will be described.
1. Polybutylene terephthalate (PBT)
As described above, PBT production methods include direct polycondensation of terephthalic acid and 1,4-butanediol and polycondensation by transesterification of dimethyl terephthalate and 1,4-butanediol. Such PBT may be obtained by any method.

The average molecular weight of PBT of the PBT resin composition according to the present invention is not limited. Moreover, the specific gravity is not specifically limited, The thing about 1.3 g / cm < ³ > normally available in the market can be used.

2. Thermally expandable graphite (TEG)
The thermally expandable graphite according to the present invention has an expansion start temperature of 285 ° C. or higher and an expansion degree of 1000 ° C. of 180 cc / g or higher (these characteristics and manufacturing method will be described in detail). The content of this TEG in the PBT resin composition is 11.0 parts by mass or more and 30 parts by mass or less with respect to 100 parts by weight of PBT. When the TEG content is too small, it becomes difficult to obtain sufficient flame retardancy even if the TEG has the above-mentioned characteristics. On the other hand, when the content of TEG is excessive, processability such as moldability is lowered, and it becomes difficult to maintain the mechanical properties and appearance of the molded product uniformly.

(1) Characteristics (a) Expansion start temperature The expansion start temperature of the TEG according to the present invention is 285 ° C or higher. This temperature is sufficiently higher than the general heating temperature of 260 ° C. in the PBT kneading / molding operation, so that it is the minimum for use as a flame retardant for imparting flame retardancy to the PBT resin composition. Meet the conditions. The temperature at which TEG starts to expand reduces the water concentration in a substance that expands TEG when it is introduced into graphite and heated (hereinafter also referred to as “expandable substance”) (in other words, sulfuric acid, etc. It is possible to increase the concentration by increasing the concentration of the component having a high expansion start temperature.

(B) Expansion degree The expansion degree of TEG concerning this invention is 180 cc / g or more as an expansion degree of 1000 degreeC. By having this degree of expansion, it is realized that the content of TEG in the PBT resin composition is 11.0 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of PBT. When the degree of expansion at 1000 ° C. is less than 180 cc / g, in order to obtain sufficient flame retardancy (that is, at least V-2 level in the UL94 combustion test), the content of TEG in the PBT resin composition is set to 100 mass of PBT. It must be more than 30 parts by mass with respect to the part. For this reason, the viscosity of a PBT resin composition increases, workability at the time of preparation or processing decreases, and when the heating temperature is increased to reduce the viscosity, deterioration of TEG cannot be ignored. From the viewpoint of highly realizing the ease of preparation and processing of the PBT resin composition, the degree of expansion of the TEG according to the present invention at 1000 ° C. is preferably 185 cc / g or more.

  The upper limit of the degree of expansion of the TEG according to the present invention at 1000 ° C. is not particularly set, but is preferably 240 cc / g or less for the following reason. That is, in order to obtain a TEG having a high degree of expansion, it is necessary to increase the amount of expandable substance introduced into the graphite. Here, since sulfuric acid or its related substance is often used as the expansive substance, TEG having an excessively high expansibility is often highly acidic. When such a highly acidic TEG is used as a flame retardant for the PBT resin composition, it is necessary to contain more alkaline earth metal compound in order to reduce the high acidity of the TEG. As a result, there is a concern that the content of TEG that can be contained in the PBT resin composition is reduced and the PBT resin composition cannot obtain desired flame retardancy. Therefore, the degree of expansion of the TEG contained in the PBT resin composition according to the present invention at 1000 ° C. is preferably 240 cc / g or less.

In addition, from the viewpoint of stably securing the above expansion range, the TEG according to the present invention preferably has the following particle size distribution.
22 mesh on: 5% or less (unit: mass% with respect to the whole TEG, the same shall apply hereinafter) Coarse particles become foreign matter in the PBT resin composition, causing cracks in the molded product of the PBT resin composition, and the molded product. There is a tendency to cause a decrease in strength.

  60 mesh pass: 15% or less Excessively fine particles are relatively likely to contain distorted crystals of graphite particles, so the degree of expansion decreases when the content of fine particles is large Tend.

(2) Graphite The thermally expandable graphite according to the present invention is not limited to the type of graphite used as a raw material. Any generally available raw material graphite such as natural graphite, pyrolytic graphite, and quiche graphite may be used. Although the shape is not particularly limited, it is preferable that the content of excessively coarse particles or excessively fine particles is relatively small for the reasons described above.

3. Production Method of Thermally Expandable Graphite The TEG according to the present invention can be produced by any production method as long as it has the above characteristics (expansion start temperature is 285 ° C. or higher and expansion degree is 180 cc / g or higher). Good. However, if manufactured by the following manufacturing method, the TEG according to the present invention can be manufactured efficiently and stably.

  The manufacturing method includes an oxidation step for performing a treatment for bringing graphite into contact with a treatment liquid described later, a drying step for washing and drying the treated graphite with water, and a neutralization step for neutralizing the graphite after the oxidation step. Prepare. This will be described in detail below.

(1) Oxidation step The treatment liquid used in the oxidation step in the production method according to the present invention contains an oxidizing agent containing sulfuric acid and hydrogen peroxide.

(A) Sulfuric acid As the sulfuric acid, concentrated sulfuric acid, anhydrous sulfuric acid, fuming sulfuric acid and the like are used. The sulfuric acid concentration is usually 95% by weight or more, preferably 98% by weight or more. The content of sulfuric acid in the treatment liquid is 90% by weight or more, preferably 95% by weight or more, particularly preferably 97% by weight. If it is less than 90% by weight, there is a possibility that the decrease in reaction rate becomes remarkable. Further, as described above, since moisture functions to lower the expansion start temperature of the thermally expandable graphite, the moisture concentration in the treatment liquid is preferably as low as possible.

  The relationship between the sulfuric acid and the raw material graphite is preferably 2 to 6 and particularly preferably around 3 as the weight ratio of sulfuric acid / raw material graphite. When this weight ratio is less than 2, the reaction rate decreases and the productivity decreases. On the other hand, if the number exceeds 6, the effect is saturated, which may be inconvenient from an economic point of view.

(B) Oxidizing agent The treatment liquid according to the present invention includes an oxidizing agent containing hydrogen peroxide.
As the hydrogen peroxide, a generally available 30 to 60% by weight aqueous solution may be used. The higher the concentration, the less moisture in the treatment liquid, so it is preferable to use 60% by weight. Since moisture functions to lower the expansion start temperature of TEG, the moisture concentration in the treatment liquid should be as low as possible.

  The amount of hydrogen peroxide contained in the oxidizing agent is preferably 3 to 8% by weight, particularly preferably 5 to 7% by weight, based on the raw material graphite, in terms of 60% by weight hydrogen peroxide. When the amount used is less than 3% by weight, the amount of the expandable substance inserted into the graphite crystal layer is reduced, and there is a possibility that a sufficient degree of expansion cannot be obtained. On the other hand, even if it exceeds 8% by weight, the effect of increasing the degree of expansion is less than that when it is 8% by weight, which may be disadvantageous from an economic viewpoint.

  The treatment liquid is prepared by adding an oxidizing agent to sulfuric acid, and the temperature of sulfuric acid during the addition is preferably 20 ° C. or lower. Further preferred is 10 ° C., and particularly preferred is 5 ° C. or less.

(C) Treatment conditions In the oxidation step according to the present invention, an expandable substance is introduced between the graphite layers by bringing the raw material graphite into contact with the treatment liquid. Although there is no restriction | limiting in the contact method, it is the simplest and safest to introduce | transduce raw material graphite into the reaction tank containing the process liquid. In this case, from the viewpoint of safety, it is preferable to add the raw material graphite little by little while stirring the treatment liquid so that the reaction does not become uncontrollable. In addition, it is preferable to use an appropriate cooling means so that the temperature of the treatment liquid does not increase excessively before and after the raw graphite is charged. The treatment liquid temperature before charging is preferably 20 ° C. or less, particularly preferably 5 ° C. or less, as in the adjustment step of the treatment liquid. Moreover, it is preferable that the process liquid temperature after addition does not exceed 80 degreeC, More preferably, it is 60 degrees C or less, Especially preferably, it is 50 degrees C or less. The reaction time after charging, that is, the contact time is preferably 60 minutes or less, and particularly preferably 20 to 40 minutes.

(2) Washing step, drying step (a) Washing step After the treatment liquid and the raw material graphite are reacted as described above, the reacted graphite is taken out from the treatment liquid and washed. As a method for taking out graphite, for example, filtration may be performed.

  Examples of the cleaning agent used for cleaning include water and organic solvents. As the organic solvent, ester, ether, alcohol, halogen, and ketone solvents are used. Examples of ester solvents include methyl acetate and ethyl acetate; ether solvents such as ethyl ether and butyl ether; alcohol solvents such as methanol, ethanol, propanol, and butanol; halogen solvents such as dichloromethane, Examples of ketone solvents such as trichloroethane include acetone, methyl ethyl ketone, and methyl isobutyl ketone.

Washing with water is preferably performed by adding the reacted graphite to a large amount of water and stirring well. Here, since a considerable amount of concentrated sulfuric acid adheres to the graphite after the reaction, there is a concern about a rapid temperature increase due to the dilution heat of concentrated sulfuric acid when it is brought into direct contact with water. Therefore, it is preferable that the graphite after the reaction taken out from the treatment liquid is once poured into a dilute sulfuric acid solution to dilute the concentrated sulfuric acid, and then filtered again, and then washed by contacting with water. The washing time with water is usually 10 to 60 minutes, preferably 20 to 30 minutes, and the water temperature is usually 20 ° C. or less, preferably 10 ° C. or less.
In the case of washing with an organic solvent, the organic solvent may react with concentrated sulfuric acid to produce an unnecessary by-product, so that it is preferable to wash with dilute sulfuric acid.

(B) Drying step When washing is completed in this way, the liquid phase is separated by filtration or the like to recover the solid content. The collected solid content is dried under a normal pressure or a reduced pressure by a known drying means such as oven drying, shelf drying, airflow drying or fluidized drying.

  The preferable lower limit of the drying temperature varies depending on the boiling point of the cleaning agent and the drying conditions (normal pressure / reduced pressure), and may be set as appropriate. One upper limit may be set so that the TEG during drying does not expand. Usually, in the case of normal pressure, it is performed at 80 to 120 ° C. Since the TEG according to the present invention has a high expansion start temperature, it may be dried by heating to about 250 ° C. in the case of normal pressure. By drying at such a high temperature in this way, it is possible to screen for an accidentally low expansion start temperature. By using the TEG thus thermally screened, problems during the production of the PBT resin composition, for example, gas generation due to expansion of the TEG, can be prevented more reliably.

(3) Neutralization Step (a) Purpose of Neutralization Since the sulfuric acid component is still adsorbed on the surface of the TEG after drying, the obtained PBT resin composition is used as it is as a raw material for the PBT resin composition. In the preparation and processing, there is a risk of corroding the kneader and the injection molding machine or decomposing the PBT in the composition. Therefore, in the present invention, the acid remaining on the surface of the TEG is neutralized by bringing the neutralizing agent containing the alkaline earth metal compound into contact with the TEG.

(B) Neutralizing agent Examples of the alkaline earth metal compound used as the neutralizing agent include alkaline earth metal oxides, hydroxides, carbonates, and organic acid salts. Examples of the alkaline earth metal oxide include beryllium oxide, magnesium oxide, and calcium oxide. Examples of the alkaline earth metal hydroxide include beryllium hydroxide, magnesium hydroxide, and calcium hydroxide. Examples of the alkaline earth metal carbonate include beryllium carbonate, magnesium carbonate, and calcium carbonate. Examples of alkaline earth metal organic acid salts include beryllium octylate, magnesium octylate, calcium octylate, beryllium naphthenate, magnesium naphthenate, calcium naphthenate, other berylliums such as phthalic acid, pyromellitic acid, trimellitic acid, Magnesium and calcium salts are exemplified.

(C) Neutralization method The neutralization method using the neutralizing agent is not particularly limited. In the cleaning step, a solution containing a neutralizing agent may be used as the cleaning agent. In this case, the neutralization process is integrated with the washing process. The graphite that has been cleaned with the cleaning agent may be brought into contact with a cleaning solution containing this neutralizing agent, or may be dried by mixing the neutralizing agent with graphite before drying. In this case, the neutralization process is an independent process between the washing process and the drying process. A neutralizing agent may be directly mixed with the graphite after drying, or the dried graphite may be brought into contact with a solution containing the neutralizing agent and then dried. In this case, the neutralization step is an independent step performed after the drying step. In consideration of productivity, it is preferable to use a solution containing a neutralizing agent as a cleaning agent during cleaning, that is, to integrate the neutralization step with the cleaning step. However, in order to avoid an adverse effect due to the heat of neutralization, it is preferable that after washing with diluted sulfuric acid and washing with water as described above, washing with this detergent and finally washing with water again.

4). Alkaline earth metal compound The PBT resin composition according to the present invention contains an alkaline earth metal compound in an amount of 0.14 parts by mass or more and 1.2 parts by mass or less in terms of alkaline earth gold with respect to 100 parts by mass of PBT.

  Since the TEG according to the present invention is usually produced by the above method, it is a strongly acidic substance derived from the sulfuric acid remaining on the TEG even though it has undergone a washing step. Therefore, when this TEG and PBT are kneaded as they are, the PBT is altered or decomposed due to the acidity of the TEG. For this reason, when kneading TEG and PBT, the alkaline earth metal compound, which is an alkaline substance, is allowed to coexist to make the kneaded material almost neutral, thereby suppressing alteration and decomposition of PBT. Therefore, the TEG according to the present invention contains an alkaline earth metal compound blended for the purpose of adjusting the pH of the kneaded product. The content is as described above, and the specific content is appropriately determined in relation to the content of TEG.

5. Phosphate ester The PBT resin composition according to the present invention contains a phosphate ester in an amount of 0.56 parts by mass or more and 5.21 parts by mass or less in terms of phosphorus with respect to 100 parts by mass of PBT.

When the PBT resin composition is heated, the phosphate ester forms an inorganic polymer composed of an oxide of phosphorus, which is disposed between the expanded TEG particles to assist the combustion prevention function by the TEG. Ensure the flame retardancy of the resin composition. Thus, since phosphoric acid ester is the positioning of the flame retardant aid, when the content of phosphoric acid ester is excessively high, the content of TEG, which is the main agent that imparts relatively flame retardancy, is relative. There is a concern that the PBT resin composition cannot be provided with sufficient flame retardancy. On the other hand, when the phosphate ester content is excessively low, the interaction with the above TEG is not sufficiently exhibited, and it is impossible to impart sufficient flame retardancy to the PBT resin composition. Concerned. From the viewpoint of imparting particularly high flame retardancy to the PBT resin composition, the phosphate ester content is preferably 2.77 parts by mass or more and 5.21 parts by mass or less in terms of phosphorus with respect to 100 parts by mass of PBT. .

  Here, as described above, the action of the phosphate ester is to complement the combustion suppressing function due to the expansion of the TEG. Therefore, the relationship between the TEG content and the phosphate ester content is phosphoric acid relative to the mass part of the TEG. The ratio by mass of the ester is preferably 0.2 or more and 3.0 or less, and particularly preferably 0.5 or more and 2.0 or less.

  In addition, since the phosphate ester is a supply source of the inorganic polymer by the oxide of phosphorus as described above, the functional group forming the ester portion is not particularly limited. Moreover, if it is a phosphoric acid ester, it does not decompose | disassemble at the time of preparation of a PBT resin composition and / or a process like red phosphorus irrespective of a functional group. However, from the viewpoint of improving the dispersibility in the PBT resin composition, the functional group forming the ester portion in the phosphate ester is preferably an aromatic group.

6). Other Components The PBT resin composition according to the present invention can further contain any component as long as it does not affect the flame retardancy. A typical example is an anti-drip agent composed of acrylic-modified PTFE. Other examples include inorganic fine particles (such as glass beads and glass fibers) for improving mechanical strength and lubricants (such as wax and solid lubricant) for improving sliding properties.

7). PBT resin composition The method for preparing the PBT resin composition is not particularly limited. PBT, TEG, alkaline earth metal compound, phosphate ester, and other components may be blended in any order and kneaded. In addition, since the alkaline earth metal compound is derived from the neutralizing agent, it is preferably a mixture with TEG at the production stage of the PBT resin composition. Further, during kneading, heating is generally performed to lower the viscosity of PBT, and the temperature is about 260 ° C. as described above.

  The obtained PBT resin composition is generally subjected to a molding process. Since the molding temperature at that time is about 260 ° C. as in the case of kneading, it is sufficient that the molded product made of the PBT resin composition according to the present invention deteriorates the flame retardancy due to deterioration of the TEG contained therein. Is suppressed.

Hereinafter, although the effect of the present invention is explained based on an example, the present invention is not limited to this.
1. Preparation of TEG The thermally expandable graphite was charged with 450 g of 98 wt% sulfuric acid (hereinafter abbreviated as “98% sulfuric acid”) in a 1 L capacity container and cooled to 5 ° C. Then, 9.0 g of a 60 wt% aqueous hydrogen peroxide solution (hereinafter abbreviated as “60% hydrogen peroxide”) kept at room temperature was added over 5 minutes to obtain a treatment liquid having a temperature of 18 ° C.

  The graphite particle size is 1% by weight for 22 mesh on, 10% by weight for 22-30 mesh, 80% for 30-60 mesh, and 9% by weight for 60 mesh pass. Then, it was added over 2 minutes, and after the addition, the reaction was held for 30 minutes. During this time, the liquid temperature rose to a maximum of 42 ° C. The weight ratio of 98% sulfuric acid / raw material graphite was 3. The weight ratio of 60% hydrogen peroxide / raw material graphite was 0.05.

The resulting dispersion of graphite-treated liquid was filtered to remove the sulfuric acid content, and the solid content collected was further dried to a moisture content of 2% or less to collect acid-treated graphite. 50 g of the recovered acid-treated graphite is mixed with 5 g of magnesium hydroxide, and the mixture is stirred to carry out a neutralization treatment to obtain a mixture of thermally expandable graphite (TEG) and an alkaline earth metal compound (hereinafter, "TEG mixture").
Thus, a TEG having an expansion start temperature of 285 ° C. and an expansion degree of 180 cc / g was obtained.

2. Preparation of test piece for evaluation Polybutylene terephthalate (PBT, Novaduran 5010R5 manufactured by Mitsubishi Engineering Plastics Co., Ltd.), TEG mixture prepared by the above method, one of the following phosphorus compounds, and drip agent (Mitsubishi) Rayon Co., Ltd. Metablen A-3800) was mixed with a twin-screw extruder (Kobe Steel Co., Ltd.) at the compounding ratios shown in Tables 1 to 3 (the numerical values for the compounding amounts in the tables all represent parts by mass). KTX-30) was used to knead at a kneading temperature of 240 to 250 ° C. to obtain cylindrical pellets having a diameter of 2 mm and a thickness of 3 mm.

In addition, the phosphorus type compound used for said pellet preparation was either of the following.
Non-halogen condensed phosphate ester: Daihachi Chemical Industry Co., Ltd. PX-202, phosphorus content 9% by mass,
Red phosphorus: Phosphorus Chemical Co., Ltd., red phosphorus 30% MB, mixture of phosphorus content 30% by weight and PBT content 70% by weight,
Ammonium polyphosphate: Iberica, TERRAJU C-60, phosphorus content 28% by weight, phosphorus content 28% by weight.

A test piece for flame retardancy test was produced from 1000 g of the obtained pellets using an injection molding machine (Nissei Plastic Industry Co., Ltd. PS-40, resin temperature: 270 ° C., mold temperature: 60 ° C.). The shape of the test piece was as follows.
125 ± 5 mm × 13.0 ± 0.5 mm × 3.0 to 3.2 mm (1/8 inch)

3. Flame Retardancy Test UNDERWRITERS LABORATORIES INC. In accordance with UL94 (plastic material combustion test for equipment and appliance parts (vertical combustion test)), one of the safety standards (UL standards) for electrical equipment established and approved by the company, Flame retardancy was evaluated.

(1) The test piece manufactured by the above method is suspended vertically.
(2) Indirect flame with a burner of a flame size determined by UL94 for 10 seconds, measure the burning time of the test piece, and install cotton (surgical cotton, 51 mm x 51 mm) 305 mm vertically below the test piece × Check the ignitability of the thickness 6.4mm).

(3) Repeat the flame contact twice.
(4) Conduct five tests.
(5) Evaluation is made based on Table 4 below. When it is V-0 to V-2, it determines with a pass. In the case of inappropriateness, “x” is displayed in Table 4.

  To summarize these evaluation criteria, in the case of V-2, the burning part drips (the burning resin composition falls), but the burning of the test piece stops. It will ignite. On the other hand, in the case of V-1 and V-0, combustion stops before drip (within 10 seconds for V-0 and within 30 seconds for V-1), so that cotton firing is also suppressed.

4). Other evaluations (1) Workability Pellets obtained by kneading and granulation and test pieces obtained by molding are extracted and visually confirmed, and mixed with pellets or test pieces that are improperly shaped such as cracks. The workability (granulation property, moldability) was evaluated according to the following evaluation criteria based on the degree of mixing (mixing rate), and “◯”, “△”, and “▲” were accepted.

(Granulation property)
Pellets are produced by cutting the filamentous resin composition (strand) extruded from the extruder into 3 mm lengths. Evaluation of the granulation property was carried out by experimentally producing 2 kg of pellets (when there is no equipment stop for adjustment, the working time is approximately 15 minutes). The evaluation criteria are as follows.

○: The self-breakage of the strand extruded from the extruder is 3 times or less, and the pellets are stably produced.
Δ: The self-breakage of the strand is 4 to 10 times, but it is not necessary to stop the apparatus, so the production of 2 kg pellets is performed without any problem (in about 15 minutes).
▲: The number of self-breakage of the strand is large and 2 kg pellets can be produced, but during that time it is necessary to stop the extruder and adjust the equipment, and the work is not completed in 15 minutes.
X: The resin composition extruded from the extruder does not form strands and cannot produce pellets.

(Moldability)
The moldability was evaluated based on how much the molding machine and the mold need to be cleaned when producing a test piece using the molding machine. The evaluation criteria are as follows.

○: The frequency of cleaning is not more than once in 10 moldings,
Δ: Multiple moldings are possible without cleaning, but the frequency of cleaning exceeds 1 in 10 times.
▲: Test piece can be molded, but cleaning is required for each molding.
X: The appearance or shape of the molded product is inferior, and the test piece cannot be molded.
In consideration of actual production, from the viewpoint of production efficiency, a resin composition that is judged as “◯” or “Δ” for both the kneading step and the molding step is preferable.

(2) Combustion time The degree of combustion is quantitatively determined by the time from the start of flame contact until the maximum degree of combustion of the test piece (max-combustion time) and the time until combustion stops (total-combustion time). Can be evaluated. If the material itself has low flame retardancy, the total-burning time is long. If the material itself has high flame retardance and is difficult to burn, the total-burning time is short and max-burning time is substantially defined. Cannot do (ND: No Drop). When the flame retardancy of the material itself is medium, the total-combustion time is long and the time to reach the max-combustion time is also long.

(3) Oxygen Index The oxygen index (Oxygen Index, JIS K7201-2) is defined by the minimum oxygen concentration (volume%) necessary for the material to continue burning. Specifically, the combustion time is continued for 180 seconds or more, or the combustion length after flame contact is determined by the minimum oxygen concentration necessary to continue burning for 50 mm or more. It is determined that a material having an oxygen concentration in air of greater than 21% cannot sustain combustion in normal air.

5. Evaluation results The results of the above evaluation are shown in Tables 1 to 3.

Claims (3)

100 parts by weight of polybutylene terephthalate,
5 parts by mass or more and 30 parts by mass or less of thermally expandable graphite having an expansion start temperature of 285 ° C. or more and an expansion degree at 1000 ° C. of 180 cc / g or more,
The alkaline earth metal compound used as a neutralizing agent is 0.14 parts by mass or more and 1.2 parts by mass or less in terms of alkaline earth metal, and the phosphoric acid ester is 0.56 parts by mass or more and 5.21 parts by mass in terms of phosphorus. flame retardant polybutylene terephthalate resin composition characterized by containing a part or less <br/>.   The composition according to claim 1, wherein the alkaline earth metal compound contains magnesium and / or calcium.   The composition according to claim 1, wherein the ratio of the phosphate ester content (unit: parts by mass) to the thermally expandable graphite content (unit: parts by mass) is 0.2 or more and 3.0 or less.