CN108794805B

CN108794805B - Halogen-free flame retardant system with synergistic effect of dialkyl dithiophosphate, organic phosphite and nitrogen-containing compound and application thereof

Info

Publication number: CN108794805B
Application number: CN201810684870.3A
Authority: CN
Inventors: 雷华; 文韵豪
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2018-06-28
Filing date: 2018-06-28
Publication date: 2020-06-19
Anticipated expiration: 2038-06-28
Also published as: CN108794805A

Abstract

The invention discloses a halogen-free flame retardant system based on the synergy of dialkyl dithiophosphate, organic phosphite and a nitrogen-containing compound, which comprises the following raw materials: 30-90% of dialkyl dithiophosphate, 8-30% of organic phosphite, 1-30% of nitrogen-containing compound and 1-10% of zinc-containing compound; the structural formula of the dialkyl dithiophosphate is shown as the following formula (I), wherein R₁、R₂Independently selected from linear alkyl or branched alkyl, the carbon number is 1-6; m is selected from Mg, Ca, Al, Sb, Sn, Ge, Ti, Fe, Zr, Zn, Ce, Bi, Sr, Mn, Li, Na, K, H or NH₄And m is 1 to 4. The halogen-free flame-retardant system has the characteristics of high flame retardance, no migration, no corrosion to equipment and the like, is well suitable for a glass fiber reinforced thermoplastic engineering plastic system, and obtains the halogen-free flame-retardant glass fiber reinforced thermoplastic engineering plastic with excellent comprehensive performance.

Description

Halogen-free flame retardant system with synergistic effect of dialkyl dithiophosphate, organic phosphite and nitrogen-containing compound and application thereof

Technical Field

The invention relates to the technical field of flame retardants, in particular to a halogen-free flame retardant system with the synergy of dialkyl dithiophosphinate, organic phosphite and a nitrogen-containing compound and application thereof in preparing halogen-free flame retardant glass fiber reinforced thermoplastic engineering plastics.

Background

The glass fiber reinforced thermoplastic engineering plastic has the performance characteristics of good rigidity and impact resistance, low warping property, high dimensional stability, good surface appearance, easy processing and forming, recoverability and the like, and is widely applied to the field of electronic and electric appliances. In the application of the fields, the flame retardant requirement is provided for the material, the thermoplastic engineering plastic is an inflammable material, and after the thermoplastic engineering plastic is compounded with the glass fiber, the glass fiber reinforced engineering plastic is easier to burn due to the wick effect of the glass fiber. Therefore, when the glass fiber reinforced engineering plastic is applied to the fields, the flame retardant problem needs to be solved, and the flame retardant difficulty is higher due to the existence of the wick effect. The thermoplastic engineering plastics mainly refer to polyester and nylon.

At present, the flame retardance of glass fiber reinforced thermoplastic engineering plastics comprises two basic flame retardant systems: halogen-based flame retardant systems and non-halogen flame retardant systems. A great deal of research shows that the glass fiber reinforced thermoplastic engineering plastic added with the brominated flame retardant can generate dense smoke, hydrogen bromide and other harmful substances during combustion to cause human body suffocation, and secondly, the halogenated flame retardant has poor electrical insulation property and is limited in application in some fields. Therefore, the development of a safe, environment-friendly and high-performance halogen-free flame retardant system for the glass fiber reinforced thermoplastic engineering plastic becomes a research hotspot, and a novel halogen-free flame retardant or flame retardant system applied to the glass fiber reinforced thermoplastic engineering plastic appears in recent years.

According to the reports of the literature, the halogen-free flame retardant applied to the glass fiber reinforced thermoplastic engineering plastic mainly comprises two main basic systems: one is red phosphorus; another class is phosphorus-nitrogen based flame retardant systems. For red phosphorus, although it has a good flame retardant effect, it faces two problems: firstly, the color of red phosphorus limits the application range, and is usually only applied to black products; and secondly, severe poisons such as phosphine and the like are easily generated in the processing process, so that the problems of environmental protection and safety are caused, and therefore, the red phosphorus is not the best choice for the glass fiber reinforced thermoplastic engineering plastic. As for a phosphorus-nitrogen flame-retardant system, the phosphorus-nitrogen flame-retardant system is a high-efficiency flame-retardant system, has high flame-retardant efficiency, avoids some defects of red phosphorus, and is a hotspot of current research.

At present, a phosphorus-nitrogen compound system based on diethyl aluminum hypophosphite, for example, a diethyl aluminum hypophosphite compound melamine polyphosphate (MPP) system, is mostly applied, and has the advantages of high phosphorus content and synergistic action of phosphorus and nitrogen, high-efficiency flame retardance of glass fiber reinforced thermoplastic engineering plastics, no product color problem, high decomposition temperature, and no generation of toxic gases such as phosphine during the high-temperature processing of the glass fiber reinforced thermoplastic engineering plastics. However, there still exist some disadvantages for phosphorus-nitrogen built systems based on diethyl aluminum hypophosphite, mainly expressed in:

firstly, the two components have certain reaction decomposition at high temperature to generate a small amount of acidic substances, the acidic substances can corrode metal parts of processing equipment, and the parts need to be replaced after a certain time, so that the problems of cost increase and production efficiency reduction are caused; secondly, the nitrogen-containing compound MPP is separated out to a certain extent, and after a product with a certain modulus is injected in the injection molding process of the material, deposits can exist on a mould, the appearance of the product can be influenced by the existence of the deposits, so that the mould needs to be stopped and cleaned, the production efficiency can be reduced, and the separation can cause the migration of the flame retardant to the surface of the product, so that the flame retardant is unevenly distributed and lost, the flame retardant of the material is finally failed, and potential safety hazards exist; and thirdly, the addition amount is large, and the influence on the mechanical property of the material is large.

In summary, the flame retardant systems currently applied to glass fiber reinforced thermoplastic engineering plastics have the problems of color, toxic gas generation, easy precipitation, corrosion, material mechanical property reduction and the like, some are fatal and cannot be used, and some are cost increase, efficiency reduction and the like. Therefore, there is a need to develop new halogen-free flame retardant systems.

Disclosure of Invention

The invention discloses a halogen-free flame-retardant compound system applied to glass fiber reinforced thermoplastic engineering plastics, aiming at the defects of the existing phosphorus-nitrogen compound flame-retardant system based on diethyl aluminum hypophosphite applied to the glass fiber reinforced thermoplastic engineering plastics.

The specific technical scheme is as follows:

a halogen-free flame retardant system with synergy of dialkyl dithiophosphate, organic phosphite and nitrogen-containing compound comprises the following raw materials by weight percent:

the dialkyl dithiophosphate has a structural formula shown as the following formula (I):

in the formula, R₁、R₂Independently selected from linear alkyl or branched alkyl, wherein the carbon number of the linear alkyl or branched alkyl is 1-6;

m is selected from Mg, Ca, Al, Sb, Sn, Ge, Ti, Fe, Zr, Zn, Ce, Bi, Sr, Mn, Li, Na, K, H or NH₄And m is 1 to 4.

The novel dialkyl dithiophosphate flame retardant is adopted, and is cooperated with inorganic phosphite and a nitrogen-containing compound to form a multi-element synergistic compound flame retardant system based on phosphorus, sulfur and nitrogen, so that the defects of easy corrosion, easy migration and precipitation and the like of the conventional compound flame retardant system based on diethyl aluminum hypophosphite in flame-retardant glass fiber reinforced thermoplastic engineering plastics are overcome. The novel flame-retardant system can be well adapted to glass fiber reinforced thermoplastic engineering plastic materials, and halogen-free flame-retardant materials with excellent performance are obtained.

Preferably, in the formula of the dialkyldithiophosphate, R₁、R₂Independently selected from methyl, ethyl, n-propyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, n-hexyl or isohexyl; m is selected from Mg, Ca, Al, Sn, Ti or Zn.

Further preferably, the dialkyldithiophosphinate is selected from aluminium diethyldithiophosphate or aluminium diisobutyldithiphosphinate.

The invention also discloses a preparation process of the dialkyl dithiophosphate, taking preparation of the dialkyl dithiophosphate as an example, the preparation process specifically comprises the following steps:

(1) reacting a dialkyl sodium hypophosphite solution with an aluminum sulfate solution under an acidic condition to obtain a suspension of the dialkyl aluminum hypophosphite precipitate;

(2) and filtering, washing and drying the suspension at 120 ℃, and crushing the suspension to a certain particle size to obtain the dialkyl aluminum dithiophosphate flame retardant.

The sodium dialkyldithiophosphate as a raw material can be obtained commercially or prepared by the following method:

(a) the linear olefin and phosphine can generate free radical addition reaction in the presence of an initiator and under certain temperature and pressure to generate dialkyl phosphine;

(b) reacting dialkyl phosphine with sulfur to generate dialkyl dithiohypophosphorous acid;

(c) the dialkyl dithiophosphinate and sodium hydroxide react to generate the water-soluble sodium dialkyl dithiophosphate.

The dialkyl dithiophosphate has the characteristics of high phosphorus content, synergy of sulfur elements, good flame retardance, higher initial decomposition temperature, extremely low water solubility, migration resistance and no moisture absorption, and is a novel engineering plastic which can be applied to nylon, polyester and the like, in particular to glass fiber reinforced engineering plastic. The single use of dialkyl dithiophosphate in some application fields has poor flame retardant performance, so the dialkyl dithiophosphate needs to be compounded with synergistic components to meet the flame retardant requirement.

The inventor finds that in the presence of dialkyl dithiophosphate, proper organic phosphite and nitrogen-containing compound are added to form a halogen-free flame retardant system mainly based on a phosphorus-sulfur-nitrogen structure, and the system has better flame retardant property.

The general structural formula of the organic phosphite is shown as the following formula (II) or the following formula (III):

in the formula, R is selected from aryl or linear aliphatic alkyl with 1-6 carbon atoms, and Me is selected from zinc, calcium or magnesium.

Preferably, the aluminum methyl phosphite and the aluminum ethyl phosphite are used, and the smaller the molecular weight of the R group is, the higher the phosphorus content is, and the more favorable the flame retardance is.

The preparation method of the organic phosphite comprises the following steps: (1) hydrolyzing organic phosphite ester under an acidic condition to prepare organic phosphite ester; (2) reacting organic phosphorous acid and metal hydroxide in an aqueous medium under an acidic condition at a high pressure of 150-180 ℃; (3) filtering, washing and drying the suspension at 200-240 ℃, and crushing to a certain particle size. The prepared organic phosphite has high thermal decomposition temperature, can act synergistically with dialkyl dithiophosphate, and has low water solubility and migration resistance.

The nitrogen-containing compound is usually a melamine derivative, contains nitrogen elements in a molecular structure, is usually an air source in a halogen-free flame retardant system, has a high thermal decomposition temperature, can be independently used as a flame retardant, but has low flame retardant efficiency and large addition amount, and needs to be cooperated with other flame retardants. The inventor researches and discovers that the nitrogen-containing compound which resists high temperature and does not precipitate is introduced into the system in a small amount, so that the corrosion resistance is solved, the flame retardance is provided, and the problem of precipitation is avoided. Preferably, the melamine derivative is selected from at least one of Melamine Cyanurate (MCA), melamine polyphosphate (MPP), melamine metal phosphite. The melamine metal phosphite is selected from calcium melamine phosphite and/or aluminum melamine phosphite.

In addition, it has been found that the incorporation of a small amount of a zinc-containing compound which is resistant to high temperatures and does not precipitate in the above system further improves corrosion resistance and thermal stability and provides flame retardancy without causing a problem of precipitation. Preferably, the zinc-containing compound is selected from zinc borate and/or zinc stannate, both of which have high decomposition temperatures, low water solubility, and do not migrate out. Can cooperate with phosphorus-sulfur structure, improve flame retardance, and has smoke suppression effect and smoke density reduction effect.

In order to further improve the synergistic flame retardant effect, in the compound system, the dialkyl dithiophosphate is powdery, and the average particle size D50 is 20-50 mu m; the organic phosphite is powder, and the average grain diameter D50 is 20-50 μm; the nitrogen-containing compound is powdery, and the average particle size D50 is 20-50 μm; the zinc-containing compound is powdery, and the average particle size D50 is 20-50 μm.

The invention also discloses a halogen-free flame-retardant glass fiber reinforced thermoplastic engineering plastic prepared by adding the halogen-free flame-retardant system, which comprises the following raw materials in percentage by weight:

the substrate is selected from polyamide or polyester.

The polyamide includes aliphatic polyamide and semi-aromatic polyamide, such as nylon 6, nylon 66, nylon MXD6, nylon 12, and high temperature nylon such as nylon 46, 4T, 6T, 9T, 10T, 12T, etc.

The polyester comprises PBT or PET.

When the substrate is selected from polyamides, the preferred raw material composition comprises:

further preferably, the halogen-free flame retardant system comprises the following raw materials:

still more preferably, the substrate is selected from PA66, the organic phosphite is selected from aluminium methylphosphite, the nitrogen containing compound is selected from melamine polyphosphate, the zinc containing compound is selected from zinc borate, and the dialkyl dithiophosphate is selected from aluminium diisobutyl dithiophosphate.

When the base material is selected from polyester, the raw material composition comprises:

still more preferably, the substrate is selected from PBT, the organic phosphite is selected from aluminium methylphosphite, the nitrogen containing compound is selected from melamine polyphosphate, the zinc containing compound is selected from zinc borate, and the dialkyl dithiophosphate is selected from aluminium diisobutyl dithiophosphate.

The halogen-free flame-retardant glass fiber reinforced thermoplastic engineering plastic prepared by the formula can reach the flame retardant grade of UL94V0(1.6mm), and has the advantages of no corrosion to equipment and no precipitation.

The invention also discloses a preparation method of the halogen-free flame-retardant glass fiber reinforced thermoplastic engineering plastic, wherein after the raw materials are blended, the flame-retardant system is uniformly dispersed in the base material, and then the components are melted and blended in an extruder through a double-screw extruder with a glass fiber feeding port and a flame retardant powder feeding port, and are extruded and granulated.

Compared with the prior art, the invention has the following advantages:

the invention discloses a halogen-free flame retardant system cooperatively compounded by dialkyl dithiophosphate, organic phosphite and phosphorus, sulfur and nitrogen multiple elements of nitrogen-containing compounds, which has the advantages of high flame retardance, no migration, no corrosion to equipment and the like, can be used as a halogen-free flame retardant system of glass fiber reinforced thermoplastic engineering plastics, and can be used for preparing novel halogen-free flame retardant glass fiber reinforced thermoplastic engineering plastics special materials applied to the field of electric and electronics.

Detailed Description

Raw materials:

(1) preparation of diisobutyldithiophosphorus phosphate

1392g of sodium diisobutyldithiophosphate aqueous solution with the concentration of 20 wt% and 228g of aluminum sulfate solution with the concentration of 30 wt% are prepared respectively, 1500g of desalted water and 75g of sulfuric acid solution with the concentration of 25 wt% are added into a reactor, the temperature is raised to 80 ℃, sodium diisobutyldithiophosphate aqueous solution and aluminum sulfate solution are synchronously dripped into the reactor according to the proportion to obtain the precipitate of the aluminum diisobutyldithiophosphate, the dripping is completed within 2 hours, the temperature is kept for 1 hour, and then the precipitate is filtered, washed and dried to obtain 254g of the aluminum diisobutyldithiophosphate flame retardant (the yield is 97%).

The test shows that the initial decomposition temperature of the product is 350 ℃, and the solubility in water is 0.02%;

(2) MPP, Melapur 200, available from BASF;

(3) zinc borate, Firebake 500, available from Borax;

(4) nylon 66, EPR27, platypodium;

(5) glass fiber, ECS301UW, Chongqing International composite Limited;

(6) diethyl aluminum hypophosphite, 8003, Jiangsu Risk new materials, Inc.;

(7) antioxidant 1098, BASF;

(8) silicone, medium blue-morning light;

(9) PBT, 211M, vinpocetine;

(10) aluminum methylphosphite, a new material of Jiangsu Liscan GmbH.

Example 1

The halogen-free flame-retardant compound system is applied to glass fiber reinforced nylon, and the performance of the flame retardant is inspected according to the following steps and test methods.

(1) Compounding of halogen-free flame retardant systems

And (3) adding the components of the compound flame-retardant system and other auxiliary agents which are weighed in advance according to the proportion into a high-speed stirring machine, starting high-speed stirring, stirring for 10min, and completing the mixing and discharging of the powder.

(2) Extrusion granulation of materials

Setting the temperature of each area of the double-screw extruder at a preset temperature, adding nylon from a hopper after the temperature is stabilized for 20min, adding glass fibers through a glass fiber adding port, feeding the powder mixed in the step (1) through a powder feeding hole, and starting a host machine and a feeding machine to complete the extrusion granulation of the material. And (4) sending the granulated materials into a storage bin through an air conveying system, and drying.

(3) Application and testing of materials

And (3) injecting the dried material into an injection molding machine to obtain standard samples specified by various test standards, and testing the performance of the related material. The following performance indicators are of primary concern:

flame retardancy test

Tested according to the UL94V0 test standard.

Migration resistance test

The prepared halogen-free flame-retardant glass fiber reinforced nylon sample is placed in a constant temperature and humidity box, the temperature is set to be 85 ℃, the relative humidity is 85%, and the state of the surface of the sample after 168 hours is observed visually.

Corrosion test

A metal block is arranged on a die head, a high-temperature material is contacted with the metal block in the die head, and the loss of the metal after 25Kg material granulation is tested, wherein the higher the loss is, the worse the corrosion resistance is. Corrosion was considered acceptable if the amount of corrosion was < 0.1%.

Mechanical Property test

Tensile strength was tested according to ASTM D638 and impact strength was tested according to ASTM D256.

The materials and the proportions in this example are shown in Table 1, and the test results of the obtained materials are shown in Table 1.

Example 2

The procedure was carried out in the same manner as in example 1, with the total amount of the flame retardant system being kept constant and the proportions of diisobutyldithiophosphonite, aluminum phosphite and MPP being adjusted. The other materials and the mixture ratio are shown in table 1, and the obtained material results are shown in table 1.

Example 3

Example 4

The implementation process is the same as that of the example 1, the total amount of the flame-retardant system is kept unchanged, the proportion of the diisobutyldithiophosphate is kept unchanged, and the proportion of other three components is adjusted. The other materials and the mixture ratio are shown in table 1, and the obtained material results are shown in table 1.

Comparative example 1

The procedure was as in example 1, except that aluminum diethylphosphinate was used in place of aluminum diisobutyldithiphosphinate. The other materials and the mixture ratio are shown in table 1, and the obtained material results are shown in table 1.

Comparative example 2

The procedure was carried out as in example 1, except that zinc borate was not used. The other materials and the mixture ratio are shown in table 1, and the obtained material results are shown in table 1.

Comparative example 3

The procedure was as in example 1, except that only diisobutyldithiophosphonite and zinc borate were used, and no aluminum phosphite was used. The other materials and the mixture ratio are shown in table 1, and the obtained material results are shown in table 1.

Comparative example 4

The procedure was as in example 1, except that only diisobutyldithiophosphonite was used. The other materials and the mixture ratio are shown in table 1, and the obtained material results are shown in table 1.

Comparative example 5

The procedure was as in example 1, except that the flame retardant system used a combination of aluminum diethylphosphinate and MPP. The other materials and the mixture ratio are shown in table 1, and the obtained material results are shown in table 1.

TABLE 1

Example 5

The procedure was as in example 1, replacing nylon 66 with PBT. The other materials and the mixture ratio are shown in the table 2, and the obtained material results are shown in the table 2.

Example 6

The procedure was carried out as in example 2, replacing nylon 66 with PBT. The other materials and the mixture ratio are shown in the table 2, and the obtained material results are shown in the table 2.

Example 7

The procedure was carried out as in example 3, replacing nylon 66 with PBT. The other materials and the mixture ratio are shown in the table 2, and the obtained material results are shown in the table 2.

Example 8

The procedure was carried out as in example 4, replacing nylon 66 with PBT. The other materials and the mixture ratio are shown in the table 2, and the obtained material results are shown in the table 2.

Comparative example 6

The procedure was the same as in comparative example 1, replacing nylon 66 with PBT. The other materials and the mixture ratio are shown in the table 2, and the obtained material results are shown in the table 2.

Comparative example 7

The procedure was the same as in comparative example 2, replacing nylon 66 with PBT. The other materials and the mixture ratio are shown in the table 2, and the obtained material results are shown in the table 2.

Comparative example 8

The procedure was carried out as in comparative example 3, replacing nylon 66 with PBT. The other materials and the mixture ratio are shown in the table 2, and the obtained material results are shown in the table 2.

Comparative example 9

The procedure was carried out as in comparative example 4, replacing nylon 66 with PBT. The other materials and the mixture ratio are shown in the table 2, and the obtained material results are shown in the table 2.

Comparative example 10

The procedure was carried out as in comparative example 5, replacing nylon 66 with PBT. The other materials and the mixture ratio are shown in the table 2, and the obtained material results are shown in the table 2.

TABLE 2

Claims

1. A halogen-free flame retardant system with synergistic effect of dialkyl dithiophosphate, organic phosphite and nitrogen-containing compound is characterized in that the halogen-free flame retardant system comprises the following raw materials by weight percent:

in the formula, R₁、R₂The carbon number of the linear alkyl or the branched alkyl is 1-6.

2. The synergistic halogen-free flame retardant system of claim 1, wherein R is selected from the group consisting of dialkyldithiophosphinate, organophosphites and nitrogen-containing compounds₁、R₂Independently selected from methyl, ethyl, n-propyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, n-hexyl or isohexyl.

3. The synergistic halogen-free flame retardant system of dialkyldithiophosphate, organophosphite and nitrogen-containing compound according to claim 1 or 2, wherein the average particle diameter D50 of the dialkyldithiophosphate is 20 to 50 μm.

4. The synergistic halogen-free flame retardant system of dialkyldithiophosphate, organophosphite and nitrogen-containing compound according to claim 1, wherein the structural formula of the organophosphite is represented by the following formula (II) or the following formula (III):

in the formula, R is selected from aryl or linear aliphatic alkyl with 1-6 carbon atoms, and Me is selected from zinc, calcium or magnesium;

the organic phosphite has an average particle diameter D50 of 20 to 50 μm.

5. The synergistic halogen-free flame retardant system of dialkyldithiophosphinate, organophosphite and nitrogen-containing compounds according to claim 1, wherein the nitrogen-containing compound is selected from melamine derivatives and has an average particle size D50 of 20 to 50 μm.

6. The synergistic halogen-free flame retardant system of dialkyldithiophosphinate, organophosphite and nitrogen-containing compounds according to claim 1, wherein the zinc-containing compound is selected from zinc borate and/or zinc stannate and has an average particle size D50 of 20 to 50 μm.

7. A halogen-free flame-retardant glass fiber reinforced thermoplastic engineering plastic is characterized by comprising the halogen-free flame-retardant system according to any one of claims 1 to 6, and the halogen-free flame-retardant system comprises the following raw materials in percentage by weight:

the substrate is selected from polyamide or polyester.

8. The halogen-free flame-retardant glass fiber reinforced thermoplastic engineering plastic as claimed in claim 7, wherein the raw materials comprise, by weight:

the substrate is selected from polyamides;

the halogen-free flame retardant system comprises the following raw materials:

9. the halogen-free flame-retardant glass fiber reinforced thermoplastic engineering plastic as claimed in claim 7, wherein the raw materials comprise, by weight:

the substrate is selected from polyester;

the halogen-free flame retardant system comprises the following raw materials:

10. the halogen-free flame-retardant glass fiber reinforced thermoplastic engineering plastic as claimed in any one of claims 7 to 9, wherein the organic phosphite is selected from aluminum methyl phosphite, the nitrogen-containing compound is selected from melamine polyphosphate, and the zinc-containing compound is selected from zinc borate.