CN101768341A - Polybutylene terephthalate halogen-free flame-retardant composite material and preparation method thereof - Google Patents

Abstract

The invention discloses a polybutylene terephthalate halogen-free flame-retardant composite material and a preparation method thereof. The invention is characterized in that according to percentage in the total weight of the composite material, 75 percent to 90 percent of polybutylene terephthalate and 5 percent to 25 percent of microencapsulated flame retardant are uniformly mixed, heated to 230 DEG C to 240 DEG C in a double-screw extruder, melted and blended, extruded, pulled into bars, cooled, cut into granules and dried; the obtained polybutylene terephthalate halogen-free flame-retardant composite material is an inorganic hybrid polymer, wherein the microencapsulated flame retardant is uniformly dispersed in the polybutylene terephthalate in the size of micrometer. The halogen-free flame-retardant composite material has an excellent flame-retardant property, and at least overcomes the following defects of the prior polybutylene terephthalate flame-retardant material technique that: the amount of the added inorganic flame retardant is large, the halogenous flame retardant has severe harm on the environment, and the low-molecular flame retardant can easily shift to the surface of the material. The invention has a broad application prospect.

Description

Polybutylene terephthalate halogen-free flame-retardant composite material and preparation method thereof

technical field

The invention belongs to the technical field of polybutylene terephthalate (hereinafter referred to as PBT) halogen-free flame-retardant composite material and its preparation method, and specifically relates to a halogen-free composite material containing PBT, a microencapsulated flame retardant and a flame-retardant synergist. Flame retardant material and its preparation method.

Background technique

PBT has excellent properties such as high heat resistance, fatigue resistance, low friction coefficient and fast crystallization speed, and is a widely used engineering plastic. However, the existing PBT materials have disadvantages such as poor flame retardancy, slow burning, and easy dripping after burning. Therefore, it is necessary to perform flame retardant treatment on PBT during its production or processing. Most of the flame retardants currently used for flame retardant PBT materials are halogen-containing systems. For example, Chinese patents CN 101195702A and CN 1563189A disclose bromine-containing compounds and antimony trioxide as the main flame retardant additives to prepare flame retardant PBT and its reinforcing materials. Although the flame retardant efficiency of halogen-containing flame retardants is very high, because they will produce a large amount of toxic smoke during combustion, some halogen-containing flame retardants will also produce carcinogens when burned, which will bring serious harm to the environment. . Red phosphorus can also be used for flame-retardant PBT materials, such as Chinese patent CN 101200576A, which uses red phosphorus as the main flame retardant to flame-retardant PBT and its reinforcing materials. The phosphorus content of red phosphorus is the highest among the phosphorus-based flame retardants. However, due to its own color problem, it is difficult to overcome, and its ignition point is low, and spontaneous combustion may occur at higher temperatures. In addition, many flame retardants have poor compatibility with polymers, especially during the use of composite materials, some low-molecular flame retardants will migrate to the surface of the product and reduce the flame retardancy of the material.

Contents of the invention

The purpose of the present invention is to propose a polybutylene terephthalate halogen-free flame-retardant composite material and preparation method thereof, to overcome the high inorganic flame retardant addition and the high and low The disadvantages of halogen-containing flame retardants are high environmental hazards and low-molecular flame retardants are easy to migrate to the surface of materials.

The polybutylene terephthalate halogen-free flame-retardant composite material of the present invention is characterized in that it contains 75-90% by weight of polybutylene terephthalate and 5-25% of microencapsulated flame-retardant Inorganic hybrid polymer of flame retardant, in which microencapsulated flame retardant is uniformly dispersed in polybutylene terephthalate with micron size; it can also contain 0-10% by weight of flame retardant synergist , 0-2% anti-dripping agent, 0-1% antioxidant and 0-5% toughening agent.

The preparation method of the polybutylene terephthalate halogen-free flame-retardant composite material of the present invention is characterized in that: according to the percentage of the total mass of the composite material, 75-90% of the polybutylene terephthalate Mix evenly with 5-25% microencapsulated flame retardant, heat to 230-240°C in a twin-screw extruder, melt and blend, then extrude, draw, cool, pelletize and dry. That is, the polybutylene terephthalate halogen-free flame-retardant composite material of the present invention is obtained.

It is also possible to add 0-10% of flame retardant synergist, 0-2% of anti-dripping agent, 0-1% of antioxidant and 0-5% of toughening agent to the raw materials before mixing. agent.

The microencapsulated flame retardant is a core-shell flame retardant coated on the surface of the phosphorus-containing flame retardant; the core-shell flame retardant is coated with 5-25% flame retardant with core-shell structure of polyurethane resin, silicone gel, epoxy resin or cross-linked waterborne polyurethane.

The phosphorus-containing flame retardant is selected from one or more of ammonium polyphosphate, melamine polyphosphate, hypophosphite, red phosphorus, and melamine pyrophosphate;

The flame retardant synergist is selected from one or more of melamine, melamine cyanurate, melem, silicate, phosphate, borate, molybdate, double hydroxide, metal oxide kind;

The anti-dripping agent is polytetrafluoroethylene powder;

The antioxidant is selected from one or more of pentaerythritol esters, isocyanurates, thiopropionates, and phosphites;

The toughening agent is selected from high polymers containing ester bonds, high polymers containing styrene groups, high polymers containing butadiene groups, and high polymers containing hydrogenated butadiene groups. one or more.

Because the present invention has adopted microencapsulated flame retardant as the intumescent flame retardant system of main additive, the flame retardant coated with organic matter or silicone gel has good compatibility with organic polymer PBT resin, so flame retardant can be more It is well dispersed in the PBT resin, and the two substances can be better integrated, so that it is difficult for the flame retardant to migrate to the surface of the material. In addition, the surface of the microencapsulated flame retardant contains a layer of water-insoluble organic matter or silicone gel, which can improve the water resistance of the flame retardant. In addition, the intumescent flame retardant system with the microencapsulated flame retardant as the main additive in the present invention is completely halogen-free and meets the requirement of being friendly to the environment. Since the shell material of the microencapsulated flame retardant used in the present invention can also exert a synergistic flame retardant effect with the inorganic phosphorus-containing flame retardant, thereby improving the flame retardant efficiency of the flame retardant, the intumescent flame retardant system adopted in the present invention It overcomes the shortcomings of the existing PBT material flame retardant technology, such as high addition of inorganic flame retardants, high environmental hazards of halogen-containing flame retardants, and easy migration of low-molecular flame retardants to the surface of the material, and has a strong application prospect.

Detailed ways

Description of drawings

Fig. 1 is a scanning electron microscope (hereinafter referred to as SEM) photograph of a PBT material containing 10% silica gel microencapsulated ammonium polyphosphate.

Figure 2 is a SEM photo of a fault in a PBT material.

Example 1:

Mix 80% of PBT resin, 13.33% of polyurethane microencapsulated ammonium polyphosphate and 6.67% of melamine cyanurate according to the percentage of the total mass of the composite material, and heat it to 230-240 in a twin-screw extruder °C, melt blending, extrusion, drawing, cooling, pelletizing and drying to obtain the polybutylene terephthalate halogen-free flame-retardant composite material of the present invention. Then the sample strips for oxygen index test and vertical combustion test are injected by the injection molding machine, and the combustion performance test is carried out. The oxygen index test is carried out according to the international standard ASTM D2863, and the vertical combustion test is carried out according to the international standard ASTMD2863. The test result shows that the standard sample with a thickness of 3.2mm can pass the vertical combustion V-0 grade, and the oxygen index is 33. However, the PBT composite material prepared by the same method with the same content and no coating flame retardant can only reach V-2 level in the vertical burning test, and the oxygen index is only 26. It can be seen that the polyurethane microencapsulated ammonium polyphosphate improves the flame retardancy of the composite material.

The vertical burning standard specimen containing microencapsulated flame retardant can still pass the vertical burning V-0 grade after being soaked in a constant temperature water bath at 80°C for 72 hours and dried. The standard spline of oxygen index decreased slightly to 31 after being treated in the same environment. However, the PBT composite with no coating flame retardant has no grade in the vertical burning test after the same environmental treatment, and the oxygen index is reduced from 26 to 24. It can be seen that polyurethane microencapsulated ammonium polyphosphate improves the water resistance of the composite.

Example 2:

According to the percentage of the total mass of the composite material, 90% of PBT resin and 10% of silica gel microencapsulated ammonium polyphosphate are evenly mixed, heated to 230-240°C in a twin-screw extruder, and melted together. After mixing, extruding, drawing, cooling, pelletizing and drying, the polybutylene terephthalate halogen-free flame-retardant composite material of the present invention is obtained. Then the sample bar for oxygen index test was injected by injection molding machine, and then the sample bar was frozen with liquid nitrogen to break it, so as to observe the fracture morphology of the material. Figure 1 shows the SEM photo of the PBT material containing 10% silica gel microencapsulated ammonium polyphosphate.

The PBT resin is heated to 230-240°C in a twin-screw extruder, melted and blended, then extruded, drawn, cooled, pelletized and dried to obtain the PBT material. Then the sample bar for oxygen index test was injected by injection molding machine, and then the sample bar was frozen with liquid nitrogen to break it, so as to observe the fracture morphology of the material.

Figure 2 shows the SEM photos of the faults of PBT materials.

Comparing the two photos, it can be seen that the silica gel microencapsulated ammonium polyphosphate is obviously dispersed in PBT with a size smaller than 10 microns, and the additive does not appear to agglomerate, indicating that the additive is evenly dispersed in PBT.

Example 3:

Mix 80% PBT resin, 13.33% silica gel microencapsulated ammonium polyphosphate and 6.67% melamine cyanurate as a percentage of the total mass of the composite material, and heat in a twin-screw extruder The polybutylene terephthalate halogen-free flame-retardant composite material of the present invention is obtained through melt blending at 230-240°C, extrusion, strand drawing, cooling, pelletizing and drying. Then the samples for oxygen index test and vertical combustion test are injected by the injection molding machine, and finally the combustion performance test is carried out. The oxygen index test is carried out according to the international standard ASTM D2863, and the vertical combustion test is carried out according to the international standard ASTM D2863. The test result shows that the standard sample with a thickness of 3.2mm can pass the vertical combustion V-0 grade, and the oxygen index is 32. However, the PBT composite material prepared by the same method with the same content and no coating flame retardant can only reach V-2 level in the vertical burning test, and the oxygen index is only 26. It can be seen that the ammonium polyphosphate microencapsulated by silica gel improves the flame retardancy of the composite material.

The vertical burning standard specimen containing microencapsulated flame retardant can still pass the vertical burning V-0 grade after being soaked in a constant temperature water bath at 80°C for 72 hours and dried. The standard spline of oxygen index decreased slightly to 31 after being treated in the same environment. However, the PBT composite with no coating flame retardant has no grade in the vertical burning test after the same environmental treatment, and the oxygen index is reduced from 26 to 24. It can be seen that the silica microencapsulated ammonium polyphosphate improves the water resistance of the composite.

Example 4:

Mix 85% PBT resin, 9.33% polyurethane gel microencapsulated ammonium polyphosphate, 4.67% melamine cyanurate and 1% organically modified montmorillonite according to the percentage of the total mass of the composite material, Heating to 230-240°C in a twin-screw extruder, melt blending, and then extruding, drawing, cooling, pelletizing and drying to obtain the polybutylene terephthalate of the present invention without Halogen flame retardant composite material. Then the samples for oxygen index test and vertical combustion test are injected by the injection molding machine, and finally the combustion performance test is carried out. The oxygen index test is carried out according to the international standard ASTM D2863, and the vertical combustion test is carried out according to the international standard ASTM D2863. The test result shows that the standard sample with a thickness of 3.2mm can pass the vertical combustion V-0 level, and the oxygen index is 30. However, the PBT composite material prepared by the same method and containing the same content of flame retardant without coating has no grade in the vertical burning test, and the oxygen index is only 23. It can be seen that the polyurethane microencapsulated ammonium polyphosphate improves the flame retardancy of the composite material.

After soaking in a constant temperature water bath at 80°C for 72 hours and drying, the vertical burning standard specimens containing microencapsulated flame retardants can pass the vertical burning V-2 level. After the standard spline of oxygen index was treated in the same environment, it decreased slightly to 28. However, the PBT composite with no coating flame retardant has no grade in the vertical burning test after the same environmental treatment, and the oxygen index is reduced from 23 to 21. It can be seen that polyurethane microencapsulated ammonium polyphosphate improves the water resistance of the composite.

Claims (9)

1. polybutylene terephthalate halogen-free flame-retardant composite material, be characterised in that it is to contain the polybutylene terephthalate of weight percent 75～90% and the inorganic hybrid polymer of 5～25% micro encapsulation fire retardant, wherein the micro encapsulation fire retardant is dispersed in the polybutylene terephthalate with the micron order size.

2. polybutylene terephthalate halogen-free flame-retardant composite material according to claim 1 is characterised in that containing weight percent is 0～10% fire retarding synergist, 0～2% anti-dripping agent, 0～1% antioxidant and 0～5% toughner.

3. the preparation method of the described polybutylene terephthalate halogen-free flame-retardant composite material of claim 1, it is characterized in that: 75～90% polybutylene terephthalate and 5～25% micro encapsulation fire retardant are mixed by the per-cent of shared matrix material total mass, in twin screw extruder, be heated to 230～240 ℃, through melt blending, again through extrude, tie rod, cooling, pelletizing and oven dry, promptly obtain polybutylene terephthalate halogen-free flame-retardant composite material of the present invention.

4. as the preparation method of polybutylene terephthalate halogen-free flame-retardant composite material as described in the claim 3, be characterised in that to add the fire retarding synergist that accounts for matrix material total mass 0～10%, 0～2% anti-dripping agent, 0～1% antioxidant and 0～5% toughner in the raw material before mixing.

5. as the preparation method of polybutylene terephthalate halogen-free flame-retardant composite material as described in the claim 3, be characterised in that described micro encapsulation fire retardant is a kind of core-shell type fire retardant that the phosphonium flame retardant top layer is coated; Described core-shell type fire retardant is the fire retardant with nucleocapsid structure that is coated with 5～25% urethane resin, silicon gel, Resins, epoxy or cross-linking aqueous urethane on the phosphonium flame retardant top layer;

Described phosphonium flame retardant is selected from one or more in ammonium polyphosphate, melamine polyphosphate, hypophosphite, red phosphorus, the melamine pyrophosphate.

6. as the preparation method of polybutylene terephthalate halogen-free flame-retardant composite material as described in the claim 3, be characterised in that described fire retarding synergist is selected from one or more in trimeric cyanamide, melamine cyanurate, melem, silicate, phosphoric acid salt, borate, molybdate, double-hydroxide, the metal oxide.

7. as the preparation method of polybutylene terephthalate halogen-free flame-retardant composite material as described in the claim 3, be characterised in that described anti-dripping agent is a polytetrafluorethylepowder powder.

8. as the preparation method of polybutylene terephthalate halogen-free flame-retardant composite material as described in the claim 3, the preparation method of polybutylene terephthalate halogen-free flame-retardant composite material is characterised in that described antioxidant is selected from one or more in pentaerythritol ester, chlorinated isocyanurates, thiopropionate, the phosphorous acid ester according to claim 1.

9. as the preparation method of polybutylene terephthalate halogen-free flame-retardant composite material as described in the claim 3, be characterised in that described toughner is selected from superpolymer, the superpolymer that contains styrene group, the superpolymer that contains butadiene that contain ester bond, in the superpolymer that contains the hydrogenant butadiene one or more.

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