CN113698703B - Filler-free stress whitening resistant polypropylene composition and preparation method and application thereof - Google Patents

Abstract

The invention discloses a non-filled stress whitening resistant polypropylene composition, and a preparation method and application thereof. The invention relates to a non-filling stress whitening resistant polypropylene composition, which comprises the following components in parts by weight: 100 parts of polypropylene, 0.25-2.5 parts of peroxide adsorption master batch, 0.7-6 parts of activated titanium dioxide, 0.1-1 part of antioxidant, 0.05-0.5 part of light stabilizer, 0.05-0.5 part of nucleating agent and 0.1-0.5 part of lubricant; the peroxide adsorption master batch is a porous molecular sieve adsorbed with peroxide initiator; the activated titanium dioxide is titanium dioxide with the surface treated by a silane coupling agent. The non-filling stress whitening resistant polypropylene composition developed by the invention takes polypropylene as matrix resin, and ensures that the polypropylene continuously performs slight micro-crosslinking by the synergistic action of components such as a silane coupling agent, titanium dioxide, peroxide adsorption master batch, an antioxidant, a lubricant and the like, thereby greatly improving the stress whitening resistant performance of the material.

Description

Filler-free stress whitening resistant polypropylene composition and preparation method and application thereof

Technical Field

The invention relates to the technical field of modified polypropylene, in particular to a non-filled stress whitening resistant polypropylene composition, and a preparation method and application thereof.

Background

Stress whitening is a phenomenon in which plastic materials develop a large number of microcrack aggregation areas under stress, and the areas become white due to the reduction of refractive index.

Polypropylene (PP) has the advantages of low density, chemical corrosion resistance, excellent physical and mechanical properties and the like, and is easy to process and form due to low price, and is widely applied to automobile interior and exterior materials. However, stress whitening is a difficult problem in the application process of the PP material due to the self structural characteristics, and often occurs when external force acts in the injection molding and assembly processes.

There are prior art reports on the research on the problem of stress whitening of PP materials. In general, the solutions generally involve the addition of components such as compatibilizers, anti-blushing agents or elastomers to polypropylene resins containing reinforcing fillers. For example, chinese patent application CN102295808A discloses a stress whitening resistant polypropylene composition which comprises 35 to 82 weight percent of polypropylene resin, 2 to 12 weight percent of compatilizer, 5 to 15 weight percent of stress whitening resistant agent, 10 to 40 weight percent of filler and other components; chinese patent application CN106700232a discloses a stress whitening resistant polypropylene resin, which comprises polypropylene resin 80-98 parts, low density polyethylene 2-20 parts, glass fiber 5-30 parts and other components. For the stress-whitening-resistant polypropylene material reported in the prior art, the reinforcing filler is generally talcum powder, mica, calcium carbonate, glass fiber, silicon dioxide and other substances, and the reinforcing filler can increase the strength and rigidity of the material and avoid the stress deformation and whitening phenomenon of the material to a certain extent.

With the development of the automobile industry, the weight reduction of automobile materials is a necessary choice in the market, but the density of polypropylene materials containing a large amount of reinforcing filler is too high to meet the weight reduction requirement. For polypropylene materials without filled reinforcing filler, the polypropylene material is more easily deformed due to the reinforcing effect of the filler, and thus stress whitening occurs. In particular to automobile interior decorative parts such as light-colored door plates, upright posts and the like, although the automobile interior decorative parts have no stress whitening phenomenon in the injection molding or assembly process, after a period of use, the automobile interior decorative parts are subjected to high and low temperature circulation and stress relaxation and are extremely easy to generate stress whitening under the action of external force.

Accordingly, there is a need to develop a polypropylene composition that is free of filler reinforcing filler and resistant to stress whitening.

Disclosure of Invention

The invention provides a non-filled stress whitening resistant polypropylene composition which has excellent stress whitening resistance on the basis of no reinforcing filler.

It is another object of the present invention to provide a process for preparing the above-described non-filled stress whitening resistant polypropylene composition.

Another object of the present invention is to provide the use of the above-mentioned non-filled stress whitening resistant polypropylene composition for the preparation of automotive interior parts.

In order to solve the technical problems, the invention adopts the following technical scheme:

the non-filled stress whitening resistant polypropylene composition comprises the following components in parts by weight:

100 parts of polypropylene, and the weight of the polypropylene,

peroxide adsorption master batch 0.25-2.5 parts,

0.7 to 6 parts of activated titanium dioxide,

0.1 to 1 part of antioxidant,

0.05 to 0.5 part of light stabilizer,

0.05 to 0.5 portion of nucleating agent,

0.1 to 0.5 part of lubricant;

the peroxide adsorption master batch is a porous molecular sieve adsorbed with peroxide initiator; the activated titanium dioxide is titanium dioxide subjected to surface treatment by a silane coupling agent.

The titanium dioxide is subjected to surface treatment by a silane coupling agent, and part of silicon oxygen bonds of the silane coupling agent participate in micro-crosslinking reaction to form silicon oxygen bonds, so that the titanium dioxide becomes a micro-crosslinking center body. After the peroxide initiator is adsorbed to the porous molecular sieve, the peroxide initiator is added in the form of peroxide adsorption master batch and is blended with other components, so that the degradation effect of the direct addition of the peroxide on the polypropylene is avoided, and meanwhile, the peroxide initiator can be continuously released at a slow rate, so that the micro-crosslinking effect is continuously carried out in the use process of the material. The silane coupling agent and the peroxide initiator in the system carry out light crosslinking on the polypropylene matrix resin, and the micro crosslinking is enabled to continuously act at a slower speed in the presence of titanium dioxide serving as a micro crosslinking central body and peroxide adsorption master batch, and the non-filling stress whitening resistant polypropylene composition can keep excellent stress whitening resistance under different conditions of use temperature, use environment and stress relaxation.

Preferably, the polypropylene is a homo-polypropylene.

Compared with the copolymerized polypropylene or the random polypropylene, the homopolymerized polypropylene has the characteristics of high crystallization and high rigidity, and has better stress whitening resistance.

Preferably, the melt flow rate of the homo-polypropylene is 2-90 g/10min at 230 ℃ and 2.16 kg.

The method for detecting the melt flow rate is according to GB/T3682-2018.

Preferably, the mass ratio of the peroxide initiator to the porous molecular sieve in the peroxide adsorption master batch is (0.2-0.5) to 1.

Preferably, the specific surface area of the porous molecular sieve is more than or equal to 300m ² And/g, the average particle diameter is 200-1500 mu m.

The detection method of the specific surface area of the porous molecular sieve comprises the following steps: GB/T19587-2004.

Preferably, the melting point of the peroxide initiator is less than or equal to 0 ℃.

More preferably, the peroxide initiator has a melting point of less than or equal to-35 ℃.

The melting point detection method is according to GB/T19466.3-2004.

The melting point of the peroxide initiator can reach below-60 ℃ and can reach above 100 ℃. The peroxide initiator with the melting point less than or equal to 0 ℃ is preferred, is in a liquid state at room temperature, and is convenient to adsorb by using a porous molecular sieve so as to achieve the slow release effect.

Preferably, the peroxide is one or more of di-tert-butyl peroxide (DTBP), di-tert-amyl peroxide (DTAP) or 3,6, 9-triethyl-3, 6, 9-trimethyl-1, 4, 7-triperoxonane (301).

Preferably, the peroxide adsorption master batch is prepared by the following method:

placing the porous molecular sieve in a closed container, sealing and vacuumizing to ensure that the vacuum degree in the closed container is less than or equal to-0.15 MPa, adding a peroxide initiator into the closed container, and obtaining the peroxide adsorption master batch through vacuum adsorption.

Preferably, the temperature of the vacuum adsorption is more than 0 ℃ and the time is more than or equal to 5min.

Preferably, the activated titanium dioxide is prepared by the following method:

dispersing titanium dioxide in the aqueous solution of the silane coupling agent, stirring, dehydrating and drying to obtain the activated titanium dioxide.

Preferably, the silane coupling agent is vinyltriethoxysilane.

Titanium dioxide is generally classified into: rutile type titanium dioxide, anatase type titanium dioxide, and titanium platelet type titanium dioxide. The rutile titanium dioxide has the characteristics of stable crystal form and compact atomic arrangement, so the titanium dioxide is preferably rutile titanium dioxide.

Preferably, the titanium dioxide is coated with a silicon aluminum coating comprising silicon oxide and aluminum oxide.

Preferably, the silicon oxide accounts for 5 to 6.5wt.% of the total mass of the titanium dioxide and the silicon aluminum coating, and the aluminum oxide accounts for 3 to 3.5wt.% of the total mass of the titanium dioxide and the silicon aluminum coating.

Because more active sites exist on the surface of the titanium dioxide, the titanium dioxide has catalytic degradation effect on polypropylene which is directly contacted with the titanium dioxide, so that the weather resistance of the titanium dioxide is reduced. In this application, after coating the titanium dioxide with an oxide having stable performance, the active site can be blocked, avoiding its negative impact on stress whitening.

Preferably, the titanium dioxide is prepared by a chlorination process, and the average particle size is less than or equal to 0.25 mu m.

More preferably, the titanium dioxide has an average particle diameter of 0.15 to 0.23 μm.

Preferably, the antioxidant can be a single antioxidant or a combination of multiple antioxidants. Preferably, the antioxidant is formed by compounding a main antioxidant and an auxiliary antioxidant.

Preferably, the primary antioxidant is a hindered phenol antioxidant; the auxiliary antioxidant is aryl phosphite antioxidant.

More preferably, the mass ratio of the main antioxidant to the auxiliary antioxidant is (0.8-1.2) to 1.

Preferably, the light stabilizer is one or more of hindered amine light stabilizer, benzophenone ultraviolet absorbent and benzotriazole ultraviolet absorbent.

Alternatively, the hindered amine light stabilizer may be selected from the group consisting of UV-944, UV-770, UV-622, and the like.

Alternatively, the benzophenone-based ultraviolet absorber can be selected from the group consisting of UV-531, UV-1200, and the like.

Alternatively, the benzotriazole-based ultraviolet absorber may be selected from the group consisting of UV-5411, UV-326, and the like.

Preferably, the nucleating agent is a beta-type nucleating agent.

The beta-type nucleating agent is an unstable crystal form, and can be changed into an alpha crystal form when external conditions change, so that the problem of stress concentration from the inside and the outside can be solved in the crystal form change process, and the stress whitening self-repairing function of the non-filled anti-stress whitening polypropylene composition is further enhanced.

More preferably, the nucleating agent is an aryl amide type β nucleating agent.

Optionally, the nucleating agent is TMB-5, N' -dicyclohexyl terephthalamide.

Preferably, the lubricant is stearic acid.

Stearic acid is used as a lubricant to provide lubrication on one hand, and can also be used as a hydrolysis supply agent for micro-crosslinking, so that the proceeding rate of the crosslinking reaction is greatly delayed, the micro-crosslinking is slowly and continuously carried out, and the micro-crosslinking reaction is continuously carried out after the filling-free stress whitening resistant polypropylene composition is prepared into a finished piece, so that the stress whitening problem of the material in the using process is effectively improved.

The invention also provides a preparation method of the non-filling stress whitening resistant polypropylene composition, which comprises the following steps:

mixing polypropylene, activated titanium dioxide, an antioxidant, a light stabilizer, a nucleating agent and a lubricant, and adding the mixture to a main feeding port of an extruder; adding the peroxide adsorption master batch to a side feeding port of an extruder;

and (3) carrying out melt mixing, extrusion granulation to obtain the non-filled stress whitening resistant polypropylene composition.

Preferably, the extruder is a double-screw extruder, the length-diameter ratio of the screw is 48-72:1, and the extrusion temperature is 180-200 ℃.

The invention also protects application of the non-filled stress whitening resistant polypropylene composition in preparation of automotive interior parts.

The automobile interior decorative part can be an automobile door plate, an automobile upright post or an automobile guard plate.

Compared with the prior art, the invention has the beneficial effects that:

the non-filling stress whitening resistant polypropylene composition developed by the invention takes polypropylene as matrix resin, and adopts silane coupling agent and peroxide to slightly micro-crosslink the polypropylene, so that the material has better mechanical property, and thus, the stress whitening resistance is excellent. Meanwhile, titanium dioxide is subjected to surface treatment by a silane coupling agent and is used as a micro-crosslinking center body; the peroxide is added in the form of adsorption master batch, so that the degradation of polypropylene is avoided, and meanwhile, the peroxide can be continuously released at a slow rate, so that the micro-crosslinking effect is continuously carried out in the use process of the material.

Under the action of continuous micro-crosslinking, the non-filled stress whitening resistant polypropylene composition can keep excellent stress whitening resistance under the conditions of high-temperature storage, low-temperature storage, high-low temperature circulating storage or stress relaxation.

Detailed Description

The invention is further described below in connection with the following detailed description.

The raw materials in examples and comparative examples are all commercially available;

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unless specifically stated otherwise, the reagents, methods and apparatus employed in the present invention are those conventional in the art.

Examples 1 to 21

Examples 1-21 provide a no-fill stress whitening polypropylene composition having the components content shown in Table 1;

wherein the peroxide master batch-1 is porous molecular sieve-1 for adsorbing DTBP, and the mass ratio of the DTBP to the porous molecular sieve-1 is 0.2:1; the peroxide master batch-2 is a porous molecular sieve-1 for adsorbing DTAP, and the mass ratio of the DTAP to the porous molecular sieve-1 is 0.2:1; the peroxide master batch-3 is a porous molecular sieve-1 for adsorbing 301, and the mass ratio of 301 to the porous molecular sieve-1 is 0.2:1; the peroxide master batch-4 is porous molecular sieve-2 for adsorbing DTBP, and the mass ratio of the DTBP to the porous molecular sieve-2 is 0.2:1; the peroxide master batch-5 is porous molecular sieve-1 for adsorbing DTBP, and the mass ratio of the DTBP to the porous molecular sieve-1 is 0.5:1; the peroxide master batch-6 is a porous molecular sieve-1 for adsorbing DTBP, and the mass ratio of the DTBP to the porous molecular sieve-1 is 0.7:1; the peroxide master batch-7 is porous molecular sieve-1 for adsorbing DCP, and the mass ratio of the DCP to the porous molecular sieve-1 is 0.2:1; the peroxide master batch-8 is porous molecular sieve-3 for adsorbing DTBP, and the mass ratio of the DTBP to the porous molecular sieve-3 is 0.2:1;

the preparation method of the peroxide master batch comprises the steps of placing a porous molecular sieve in a closed container, sealing, vacuumizing to ensure that the vacuum degree in the closed container is less than or equal to-0.15 MPa, adding a peroxide initiator into the closed container, and performing vacuum adsorption at 20 ℃ for 10min to obtain the peroxide adsorption master batch;

the activated titanium dioxide-1 is titanium dioxide-1 subjected to surface treatment by a silane coupling agent, the activated titanium dioxide-2 is titanium dioxide-2 subjected to surface treatment by the silane coupling agent, and the activated titanium dioxide-3 is titanium dioxide-3 subjected to surface treatment by the silane coupling agent; the activated titanium dioxide-4 is titanium dioxide-4 subjected to surface treatment by a silane coupling agent, and the activated titanium dioxide-5 is titanium dioxide-5 subjected to surface treatment by the silane coupling agent;

the preparation method of the activated titanium dioxide comprises the steps of dispersing the titanium dioxide in an aqueous solution of a silane coupling agent, stirring, dehydrating, drying and grading to obtain the activated titanium dioxide.

The preparation method of the non-filled stress whitening resistant polypropylene compositions of examples 1 to 15 is as follows:

mixing polypropylene, activated titanium dioxide, an antioxidant, a light stabilizer, a nucleating agent and a lubricant, and adding the mixture to a main feeding port of a double-screw extruder; adding the peroxide adsorption master batch to a side feeding port of a double-screw extruder; the non-filling stress whitening resistant polypropylene composition is obtained through melt mixing, extrusion granulation;

wherein the length-diameter ratio of the screws of the double screw extruder is 48-72:1, and the extrusion temperature is 180-200 ℃.

TABLE 1 component content (parts by weight) of Filler-less stress whitening resistant Polypropylene compositions of examples 1 to 21

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Comparative examples 1 to 7

Comparative examples 1 to 7 provide polypropylene compositions having the following components in amounts shown in Table 2:

mixing polypropylene, activated titanium dioxide (or titanium dioxide which is not treated by a silane coupling agent), an antioxidant, a light stabilizer, a nucleating agent and a lubricant, and adding the mixture to a main feeding port of a double-screw extruder; adding peroxide adsorption master batch (or peroxide initiator) to a side feeding port of a double-screw extruder; obtaining a polypropylene composition through melt mixing, extrusion and granulation;

wherein the length-diameter ratio of the screws of the double screw extruder is 48-72:1, and the extrusion temperature is 180-200 ℃.

Table 2 comparative examples 1 to 7 component contents (parts by weight) of the polypropylene compositions

Performance test:

the polypropylene compositions prepared in the above examples and comparative examples were injection molded into test square boards of 100 x 3mm, and the stress whitening performance was tested under the conditions of injection molding completion initiation, high temperature placement, low temperature placement, high and low temperature cyclic placement and stress relaxation, respectively, as follows:

stress whitening performance: and (3) adopting a ball falling method, freely falling 500g of balls onto the test square plate at the height of 500mm, placing the test square plate for 48 hours under standard experiment conditions (23+/-2 ℃ and relative humidity 50+/-5%), and comparing the color change conditions (delta L) of the ball falling position and the non-ball falling position of the test square plate, wherein delta L is less than or equal to 1.0, and the stress whitening resistance is good.

Initial conditions: the temperature is 23 ℃, and the mixture is placed for 48 hours;

high temperature placing conditions: placing for 400 hours at 110 ℃, and then placing for 48 hours under standard experimental conditions for stress whitening performance test;

low temperature standing conditions: placing for 400 hours at the temperature of-40 ℃, and then placing for 48 hours under standard experimental conditions for stress whitening performance test;

high-low temperature cyclic placement condition: placing at 110 ℃ for 3 hours, at 23 ℃ for 0.5 hours, at-40 ℃ for 2 hours, at 23 ℃ for 0.5 hours, performing ten cycles in total, and performing stress whitening performance test after placing for 48 hours under standard experimental conditions;

stress relaxation conditions: bending the test square plate by 30 degrees, fixing the test square plate with a clamp, placing the test square plate under standard experimental conditions for 48 hours, removing the clamp, and then placing the test square plate under standard experimental conditions for 48 hours to perform stress whitening performance test.

The test results were as follows:

TABLE 3 test results for examples 1-21

Table 4 test results of comparative examples 1 to 7

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According to the test results of Table 3, the non-filled anti-stress whitening polypropylene composition of each embodiment of the present invention has a DeltaL of 1 or less under the conditions of initial, high temperature, low temperature, high and low temperature cyclic and stress relaxation, which indicates that the non-filled anti-stress whitening polypropylene composition of the present application has excellent anti-stress whitening performance.

When the mass ratio of the peroxide initiator to the porous molecular sieve in the peroxide adsorption master batch is (0.2-0.5) to 1 in examples 1, the porous molecular sieve can more fully adsorb the peroxide initiator, and the prepared filling-free stress whitening-resistant polypropylene composition has better stress whitening resistance.

From examples 1, 2, 3 and 7, when the melting point of the peroxide initiator in example 7 is more than or equal to 0 ℃, the adsorption of the peroxide initiator by the porous molecular sieve is incomplete at room temperature, so that the stress whitening resistance of example 7 is slightly worse than that of examples 1 to 3.

From examples 1, 9, 10 and 20, the activated titanium dioxide-1 used in example 1 had a particle size of 0.2 μm and was coated with a silica-alumina coating; the activated titanium dioxide used in example 9, titanium dioxide-2, had a particle size of 0.35 μm and was coated with a silica-alumina coating; the activated titanium dioxide used in example 10 had a particle size of 0.2 μm and was free of a silica alumina coating; the particle size of the titanium dioxide in the activated titanium dioxide-5 used in example 20 was 0.2. Mu.m, with only the alumina coating. The Δl value of example 1 is relatively lowest based on the test results of the stress whitening resistance. The particle size of the titanium dioxide is less than or equal to 0.25 mu m, and when the silicon aluminum coating is coated, the prepared polypropylene composition has better stress whitening resistance.

From examples 1 and 21, the polypropylene composition obtained was more excellent in stress whitening resistance when the nucleating agent was an aryl amide type β nucleating agent.

According to the test results of Table 4, comparative example 1 does not contain titanium dioxide or activated titanium dioxide, comparative example 3 does not contain peroxide adsorption master batch, and the polypropylene composition is poor in stress whitening resistance, and has a DeltaL of 3 or more under certain standing conditions. The titanium dioxide in comparative example 2 is not treated by the silane coupling agent, so that the micro-crosslinking effect of the polypropylene composition is poor, and delta L is not less than 1 except the initial condition and cannot meet the requirement. In comparative example 4, the peroxide initiator was not added in the form of master batch, but was directly blended with other components, which resulted in easy degradation of polypropylene, and the peroxide initiator was released too quickly to continue micro-crosslinking, and the polypropylene composition reached 3.7 by placing at high temperature and reached 3.8 by relaxing the stress Δl. The comparative example 5, which does not contain a nucleating agent, makes the polypropylene composition inferior in self-repairing property of stress whitening, and Δl after being left at high and low temperature cycles is 1.5. In comparative example 6, the peroxide master batch is more, and the crosslinking rate of the polypropylene composition is too high, which is unfavorable for continuous and slow micro-crosslinking, so that the stress whitening resistance of the polypropylene composition is poor. In comparative example 7, the activated titanium dioxide content was too high, and the polypropylene composition was excellent in stress whitening resistance under the initial conditions, but after high-temperature setting, high-low temperature cycle setting or stress relaxation, the Δl was 1.0 or more, and the stress whitening resistance was poor.

It is to be understood that the above examples of the present invention are provided by way of illustration only and not by way of limitation of the embodiments of the present invention. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the invention are desired to be protected by the following claims.

Claims (5)

1. The non-filled stress whitening resistant polypropylene composition is characterized by comprising the following components in parts by weight:

100 parts of polypropylene, 0.25-2.5 parts of peroxide adsorption master batch, 0.7-6 parts of activated titanium dioxide, 0.1-1 part of antioxidant, 0.05-0.5 part of light stabilizer, 0.05-0.5 part of nucleating agent and 0.1-0.5 part of lubricant;

the peroxide adsorption master batch is a porous molecular sieve adsorbed with peroxide initiator; the activated titanium dioxide is titanium dioxide with the surface treated by a silane coupling agent;

the titanium dioxide is coated with a silicon-aluminum coating, and the silicon-aluminum coating comprises silicon oxide and aluminum oxide;

the grain diameter of the titanium dioxide is less than or equal to 0.25 mu m;

the mass ratio of the peroxide initiator to the porous molecular sieve in the peroxide adsorption master batch is (0.2-0.5) to 1;

the specific surface area of the porous molecular sieve is more than or equal to 300m ² /g, wherein the average particle size is 200-1500 μm;

the melting point of the peroxide initiator is less than or equal to 0 ℃;

the silicon oxide accounts for 5-6.5 wt.% of the total mass of the titanium dioxide and the silicon aluminum coating, and the aluminum oxide accounts for 3-3.5 wt.% of the total mass of the titanium dioxide and the silicon aluminum coating;

the nucleating agent is beta-type nucleating agent.

2. The filled stress whitening resistant polypropylene composition according to claim 1, wherein the nucleating agent is an aryl amide type β nucleating agent.

3. The no-fill stress whitening polypropylene composition according to claim 1, wherein the peroxide-based initiator has a melting point of-35 ℃.

4. A method for preparing the non-filled stress whitening resistant polypropylene composition according to any one of claims 1 to 3, comprising the steps of:

mixing polypropylene, activated titanium dioxide, an antioxidant, a light stabilizer, a nucleating agent and a lubricant, and adding the mixture to a main feeding port of an extruder; adding the peroxide adsorption master batch to a side feeding port of an extruder;

and (3) carrying out melt mixing, extrusion granulation to obtain the non-filled stress whitening resistant polypropylene composition.

5. Use of the non-filled stress whitening resistant polypropylene composition according to any of claims 1 to 3 for the preparation of automotive interior parts.