A polypropylene composition and its preparation method and application

Abstract

The invention discloses a polypropylene composition and a preparation method and application thereof. The polypropylene composition comprises the following components by weight: 90-95 parts of polypropylene; 1-2 parts of hypophosphite; 0.5-2 parts of bromine flame retardant; 0.2-0.5 parts of flame retardant synergist; 0.1-0.4 parts of primary antioxidant; 0.1-0.4 parts of auxiliary antioxidant; 0.2-0.4 parts of hindered amine light stabilizer other than N-substituted alkoxy hindered amine; the flame retardant synergist is one or more of N-substituted alkoxy hindered amines. The polypropylene composition provided by the invention has the advantages of high temperature failure resistance, long powdering time and not easy to change color during processing.

Description

Technical Field

[0001] The invention relates to the technical field of modified materials, and in particular to a polypropylene composition and a preparation method and application thereof. Background Art

[0002] Polypropylene has good processing performance and excellent mechanical, physical and chemical properties, and is light and cheap, so it is widely used in many industries such as automotive interior and exterior decoration, household appliances and electronics, packaging, textiles, building materials, automobiles, electronics / electrical, office supplies and daily necessities. However, polypropylene is very easy to burn, and its limiting oxygen index is only 17.0-18.0%. It cannot extinguish itself after catching fire in the air, which is easy to cause fire hazards, so it needs to be flame-retardant modified.

[0003] For household appliances, automobile parts, electrical components, etc., the industry generally adopts UL94 V-2 flame retardant grade. Traditional flame retardant V-2 polypropylene generally uses brominated flame retardants such as tetrabromobisphenol A-bis(2,3-dibromopropyl) ether, tetrabromobisphenol S-bis(2,3-dibromopropyl) ether or tris(2,3-dibromopropyl) isocyanurate, which is compounded with antimony trioxide. However, its disadvantage is that the brominated flame retardant used has poor compatibility with the PP resin substrate and is easy to migrate to the PP surface (blooming), which seriously affects the appearance of the parts. Moreover, brominated flame retardant products, especially tetrabromobisphenol A-bis(2,3-dibromopropyl) ether and tetrabromobisphenol S-bis(2,3-dibromopropyl) ether flame retardant systems, have poor heat resistance during injection molding and are easy to yellow during processing; finally, the bromine-antimony synergistic flame retardant system will produce a lot of thick smoke when burning, which may reduce the chance of escape in actual application.

[0004] Another flame retardant system is the phosphorus-nitrogen-bromine free radical-initiated flame retardant system, in which the bromine flame retardant is melamine hydrobromide, and the phosphorus flame retardant is metal hypophosphite (phosphonate). Most of these products on the market use 2,3-dimethyl-2,3-diphenylbutane as the free radical initiator. The total flame retardant addition of 1-2% can reach the UL94V-2 flame retardant effect, and the flame retardant system does not precipitate the "blooming" phenomenon. However, long-term use at high temperatures will cause the flame retardant efficiency of flame-retardant polypropylene to decrease, and if the temperature rises above 100°C, its service life will be even shorter.

[0005] Therefore, it is of great significance to avoid the problems of flame retardant polypropylene materials such as easy flame retardancy failure at high temperatures, short service life, easy powdering, and easy discoloration during processing. Summary of the invention

[0006] In order to overcome the above-mentioned defects of the prior art, the present invention provides a polypropylene composition and a preparation method and application thereof.

[0007] This is achieved specifically through the following technical solutions:

[0008] A polypropylene composition, comprising the following components in parts by weight:

[0009]

[0010] The flame retardant synergist is one or more N-substituted alkoxy hindered amines; and the pKa value of the hindered amine light stabilizer other than the N-substituted alkoxy hindered amine is less than 8.1.

[0011] Further, the polypropylene is selected from one or more of homopolymer polypropylene, propylene-ethylene block copolymer, propylene-ethylene random copolymer and propylene-1-butene random block. The polypropylene melt flow rate is 8 to 18 g / 10 min. The melt flow rate is tested according to ISO 1133-2-2011, the test conditions are 230° C., and the load is 2.16 kg.

[0012] Furthermore, the hypophosphite may be one or more of sodium hypophosphite, aluminum hypophosphite, calcium hypophosphite, organic aluminum hypophosphite and organic lithium hypophosphite. 50 The particle size is 10-30μm.

[0013] Furthermore, the flame retardant synergist is one or more of N-substituted alkoxy hindered amines. Since common flame retardant synergists decompose and volatilize during the thermal oxidative aging process, resulting in the attenuation of the flame retardant function of the entire system, the flame retardant synergist selected in the present invention has low decomposition volatility and high decomposition temperature, thereby improving the flame retardant failure problem.

[0014] Furthermore, the N-substituted alkoxy hindered amine is one or more of tris(1-methoxy-2,2,6,6-tetramethylpiperidin-4-yl)phosphite, bis(1-methoxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate or bis(1-alkoxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate.

[0015] Further, the primary antioxidant is one or more of tetrakis[β-(3,5-di-tert-butyl 4-hydroxyphenyl) propionate] pentaerythritol ester, tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-tris(4-tert-butyl-3-hydroxy-2.6-dimethylbenzyl) isocyanurate, ethylene bis(ethylene oxide)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl) propionate] and 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane, preferably tetrakis[β-(3,5-di-tert-butyl 4-hydroxyphenyl) propionate] pentaerythritol ester.

[0016] Further, the auxiliary antioxidant is one or more of 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate, triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl), pentaerythritol bis(diphosphite)(2,4-tert-butylphenyl)ester or thioester antioxidant, preferably thioester auxiliary antioxidant. By selecting the primary antioxidant and thioester auxiliary antioxidant, it is beneficial to form intermolecular hydrogen bond association between the phenolic hydroxyl group of the symmetrical hindered phenol antioxidant and the thioester, which is beneficial to effectively decompose the polymer hydroperoxide and convert it into a stable alcohol product, thereby improving the high temperature flame retardant failure resistance of the material.

[0017] Furthermore, the thioester antioxidant is at least one of dialkyl esters of thiodipropionic acid or pentaerythritol tetrakis (3-lauryl thiopropionate), preferably dialkyl esters of thiodipropionic acid.

[0018] Furthermore, the pKa value of the hindered amine light stabilizer is less than 8.1. For example, the high molecular weight low alkalinity hindered amine light stabilizer N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine methylated polymer with morpholine-2,4,6-trichloro-1,3,5-triazine (CYASORB UV-3529) (pKa=8.1) produced by Cytec, the Uvinul 5050H (pKa=7.5) produced by BASF (China), etc. The use of hindered amine light stabilizers with alkalinity lower than 8.1 is not easy to react with acidic substances produced by flame retardants to reduce the effect of the light stabilizer.

[0019] Furthermore, the brominated flame retardant is one or more of the bromine-phosphorus flame retardants tris(tribromoneopentyl) phosphate, tetrabromobisphenol A-bis(2,3-dibromopropyl ether), tris(2,3-dibromopropyl) isocyanurate, tetrabromobisphenol S bis(2,3-dibromopropyl) ether, melamine hydrobromide and 1,2-bis(pentabromophenyl)ethane.

[0020] Furthermore, the general structural formula of the hindered amine light stabilizer other than the N-substituted alkoxy hindered amine is:

[0021]

[0022] Wherein, X is CH3, -CH2CH3, -OCHCH3 or

[0023] When X in the above structural formula is replaced by H, the basicity of the hindered amine light stabilizer is relatively strong, and it is easy to react with the acidic flame retardant, thereby consuming the hindered amine light stabilizer, resulting in a weakened light aging protection effect on the material.

[0024] Further, the structure of the hindered amine light stabilizer other than the N-substituted alkoxy hindered amine is:

[0025]

[0026] The CAS number is 65447-77-0.

[0027] The present invention also provides a method for preparing the polypropylene composition, comprising the following steps:

[0028] S1: weigh and pre-mix the components according to the ratio to obtain a premix;

[0029] S2: putting the premix of step S1 into an extruder, performing melt blending and extrusion granulation to obtain the polypropylene composition.

[0030] Furthermore, the extruder is a twin-screw extruder, the screw speed of the twin-screw extruder is 250-350rpm, the temperatures of each section of the screw of the twin-screw extruder from the feeding port to the die are 150-160°C in zone one, 180-190°C in zone two, 180-190°C in zone three, 180-190°C in zone four, and 180-190°C in zone five, the die temperature is 190-200°C, the main engine speed is 300-500r / min, and the vacuum degree is lower than 0.1MPa.

[0031] The present invention also provides application of the polypropylene composition in the preparation of vehicles and household appliances.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] By selecting a specific flame retardant synergist and combining the flame retardant synergist with an antioxidant, the effect of the flame retardant synergist on the chain scission of polypropylene can be slowed down, the material pulverization problem can be alleviated, and the time of flame retardant failure can be extended. In the presence of a hindered amine light stabilizer, the degradation of polypropylene caused by further oxidation of aldehydes to acids can be prevented. On the one hand, the pulverization performance of the material is improved, and on the other hand, the discoloration of the material is improved. The flame retardant synergist of the present invention affects processing and thermal oxidative aging, which are the main factors of combustion failure. By selecting an antioxidant that can be used under high temperature conditions to extend the pulverization time, and then adding a hindered amine light stabilizer that can cooperate with the antioxidant, the material pulverization is extended and the discoloration is alleviated. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] <Preparation of Examples and Comparative Examples>

[0036] The raw materials used in the examples and comparative examples of the present invention are all commercially available, but are not limited to these materials:

[0037] Polypropylene: homopolymer polypropylene, PP Moplen HP500N, LyondellBasell;

[0038] Hypophosphite: aluminum hypophosphite, HT-220 (D50 = 15 μm), Shandong Taixing New Materials Co., Ltd.;

[0039] Brominated flame retardant A: melamine hydrobromide, MHB, Nanjing Yite;

[0040] Brominated flame retardant B: Tetrabromobisphenol S-bis(2,3-dibromopropyl) ether, Inner Mongolia Pulitai Material Technology Co., Ltd.

[0041] Flame retardant synergist A: tris(1-methoxy-2,2,6,6-tetramethylpiperidin-4-yl)phosphite (NORPM), Qingdao University;

[0042] Flame retardant synergist B: bis(1-methoxy-2,2,6,6-tetramethylpiperidin-4-yl) sebacate (NORSM), Qingdao University;

[0043] Flame retardant synergist C: 2,3-dimethyl-2,3-diphenylbutane, Wuxi Zhufeng Fine Chemical Co., Ltd.;

[0044] Flame retardant synergist D: p-isopropylbenzene polymer (C12H18)x, x=3-5, Wuxi Zhufeng Fine Chemical Co., Ltd.;

[0045] Primary antioxidant: pentaerythritol tetrakis[β-(3,5-di-tert-butyl 4-hydroxyphenyl) propionate, Irganox 1010, BASF, Germany;

[0046] Auxiliary antioxidant A: triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl), Irganox 168, BASF, Germany;

[0047] Auxiliary antioxidant B: dialkyl ester of thiodipropionic acid, PS802FL, BASF, Germany;

[0048] Auxiliary antioxidant C: bis(2,4-di-tert-butylphenyl) propionate] pentaerythritol diphosphite, antioxidant 626, Lianlong New Materials Co., Ltd.;

[0049] Hindered amine light stabilizer A: reaction product of α-olefin (C20-C24) containing polymer of maleic anhydride and 2,2,6,6-tetramethyl-4-piperidine, Uvinul 5050H (pKa=7.5), BASF (China);

[0050] Hindered amine light stabilizer B: poly{[6-[(1,1,3,3-tetramethylbutyl)amino]]-1,3,5-triazine-2,4-[(2,2,6,6,-tetramethyl-piperidinyl)imino]-1,6-hexanediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]}, CHIMASSORB 944FDL, pKa=8.6, BASF (China);

[0051] Hindered amine light stabilizer C: polymer of succinic acid and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol, the structure of which is:

[0052]

[0053] The CAS number is 65447-77-0, the number average molecular weight is 3000-4000, 622, pKa=5.6, BASF Schweiz AG. The preparation methods of the examples and comparative examples of the present invention are as follows:

[0054] S1: According to the ratios in Table 1 and Table 3, weigh and pre-mix the components to obtain a premix;

[0055] S2: The premix of step S1 is put into a twin-screw extruder for melt blending and extrusion granulation to obtain a polypropylene composition.

[0056] The screw speed of the twin-screw extruder is 300rpm, and the temperatures of each section of the screw of the twin-screw extruder from the feeding port to the die are 150℃ in zone 1, 180℃ in zone 2, 180℃ in zone 3, 180℃ in zone 4, and 180℃ in zone 5, respectively. The die temperature is 200℃, the main engine speed is 400r / min, and the vacuum degree is less than 0.1MPa.

[0057] <Test Standard>

[0058] The performance test standards of the embodiments and comparative examples of the present invention are as follows:

[0059] Pka test method:

[0060] Add approximately 60 ml of 0.100 mol·L-1 hexafluoropropanol (use oxalic acid if measuring weak acids with pKa < 2.3) to a dry 150 ml beaker, rinse the burette with the solution, and then fill it to 0.00 ml. Accurately release a certain volume of solution (49.95 ml in this experiment) into another clean and dry 150 ml beaker.

[0061] Place the electromagnetic stirrer in the solution, place the beaker on the electromagnetic stirrer, carefully insert the pH electrode calomel electrode into the solution, and connect it to the potentiometer to record the initial pH value.

[0062] Draw a pH-V curve. When starting the titration, record the pH value every time 1 ml of NaOH is added until the slope of the curve approaches 1.0, then change the alkali solution to record the pH value every time 0.20 ml is added until the slope of the curve approaches infinity, which is the end point. Repeat the titration twice to determine the exact end point volume.

[0063] Find the pKa from the curve. From the pH-V curve, you can find the exact value corresponding to the halfway point of the titrant from the titration endpoint. The corresponding pH value is the apparent pKa.

[0064] Powdering time: According to ASTM D5423-93 (2005), the air exchange rate is 5-20 times / hour in an oven, the temperature is set at 150°C, and the test specimen strip size is: 100mm×100mm×0.80mm. The time required for the surface of the square plate to crack or powder by 10%;

[0065] Flame retardant failure time: According to ASTM D5423-93 (2005), the ventilation frequency is 5-20 times / hour in an oven, the temperature is set to 150°C, and the combustion specimens with a size of 125mm×13mm×1.6mm and 125mm×13mm×3.2mm are baked. Then, the combustion specimens are regularly extracted to test the flame retardant performance according to UL94-2016; the first flame time in the UL94 test process is recorded as t1, and the second flame time is t2. The shorter t1+t2 is, the better the combustion performance is; the flame retardant failure is judged based on the ∑(t1+t2) time of 5 specimens tested by UL94, and it is considered to be flame retardant failure if it is greater than 250 seconds.

[0066] Yellowing index: Set the temperature of the 160-ton injection molding machine to 190°C, let the material stay in the single screw for 3 minutes, and injection mold a 100mm×100mm×2.00mm square plate. Test the yellowing index according to HG / T 3862-2006 Plastic Yellowness Index Test Method Standard.

[0067] Table 1. Formula of Examples 1-8 (parts by weight)

[0068]

[0069]

[0070] Table 2. Performance test results of Examples 1-8

[0071]

[0072] Table 3. Comparative Examples 1-8 formulations (parts by weight)

[0073]

[0074]

[0075] Table 4. Performance test results of comparative examples 1-8

[0076]

[0077] The polypropylene composition provided by the present invention has a powdering time of more than 550 hours, a powdering flame retardant performance @1.60 mm of less than 28 seconds, a powdering flame retardant performance @3.20 mm of less than 46 seconds, a yellowing index of less than 30, and has the advantages of high temperature failure resistance, a long powdering time, and not easy to change color during processing.

[0078] Compared with Example 1, the amount of the flame retardant synergist used in Comparative Example 1 is too small, resulting in a shorter powdering time of Comparative Example 1, powdering flame retardant failure, longer flame retardant failure time @1.60mm and flame retardant failure time @3.20mm, and an increase in the yellowing index; the amount of the flame retardant synergist used in Comparative Example 2 exceeds the upper limit, resulting in a shorter powdering time of Comparative Example 2, a longer flame retardant failure time @1.60mm, and an increase in the yellowing index.

[0079] Compared with Example 1, Comparative Example 3 did not add a flame retardant synergist, and Comparative Example 3 failed to pulverize and flame retardant.

[0080] Compared with Example 1, Comparative Example 4 does not add hindered amine light stabilizer. The powdering time of Comparative Example 4 is shortened and the yellowing index is increased.

[0081] Compared with the embodiment, the comparative examples 5 and 6 use inappropriate flame retardant synergists, which result in high temperature flame retardancy failure, easy powdering, and increased yellowing index of the comparative examples 5 and 6.

[0082] The difference between Comparative Example 7 and Example 3 is that the pKa of the hindered amine light stabilizer used in Comparative Example 7 exceeds 8.1, the chalking time of Comparative Example 7 is shortened, the chalking flame retardant fails, and the yellowing index increases.

[0083] Compared with Example 1, Comparative Example 8 does not add a flame retardant synergist, but the total amount of hindered amine substances remains unchanged. It can be seen that Comparative Example 8 is prone to flame retardant failure. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A polypropylene composition, characterized in that By weight, it includes the following components: The flame retardant synergist is one or more N-substituted alkoxy hindered amines; the pKa value of the hindered amine light stabilizer other than the N-substituted alkoxy hindered amine is less than 8.1; The auxiliary antioxidant is one or more of 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate, triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl), pentaerythritol bis(diphosphite) (2,4-tert-butylphenyl) ester or thioester antioxidant; The structure of the hindered amine light stabilizer other than the N-substituted alkoxy hindered amine is: The CAS number is 65447-77-0; Or the hindered amine light stabilizer other than the N-substituted alkoxy hindered amine is Uvinul 5050H。 2. The polypropylene composition according to claim 1, characterized in that The polypropylene is selected from one or more of homopolypropylene, propylene-ethylene block copolymer, propylene-ethylene random copolymer and propylene-1-butene random block, and the polypropylene melt flow rate is 8 to 18 g / 10 min; the melt flow rate is tested according to ISO 1133-2-2011, the test conditions are 230° C., and the load is 2.16 kg.

3. The polypropylene composition according to claim 2, characterized in that The N-substituted alkoxy hindered amine is one or more of tris(1-methoxy-2,2,6,6-tetramethylpiperidin-4-yl)phosphite, bis(1-methoxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate or bis(1-alkoxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate.

4. The polypropylene composition according to claim 1, characterized in that The primary antioxidant is one or more of tetrakis[β-(3,5-di-tert-butyl 4-hydroxyphenyl) propionate] pentaerythritol ester, tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-tris(4-tert-butyl-3-hydroxy-2.6-dimethylbenzyl) isocyanurate, ethylene bis(ethylene oxide)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl) propionate] and 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane.

5. The polypropylene composition according to claim 1, characterized in that The thioester antioxidant is at least one of dialkyl esters of thiodipropionic acid or pentaerythritol tetrakis (3-laurylthiopropionate).

6. The polypropylene composition according to claim 1, characterized in that The brominated flame retardant is one or more of tris(tribromoneopentyl) phosphate, tetrabromobisphenol A-bis(2,3-dibromopropyl) ether, tris(2,3-dibromopropyl) isocyanurate, tetrabromobisphenol S-bis(2,3-dibromopropyl) ether, melamine hydrobromide and 1,2-bis(pentabromophenyl)ethane.

7. A method for preparing a polypropylene composition according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: According to the ratio, weigh and pre-mix the components to obtain a premix; S2: putting the premix of step S1 into an extruder, performing melt blending and extrusion granulation to obtain the polypropylene composition.

8. Use of the polypropylene composition according to any one of claims 1 to 6 in the preparation of vehicles and household appliances.

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