A low melt index and low shrinkage PPH sheet and preparation method thereof

Abstract

The present invention belongs to the technical field of functional polymer materials, and discloses a low melt index and low shrinkage PPH sheet and a preparation method thereof. The preparation method comprises the following steps: adding homopolymerized polypropylene and organic-inorganic composite β-nucleating agent-reinforced particles into an extruder for uniform melt blending, then extruding into a mold, rapidly quenching to an isothermal crystallization temperature at a rate of 30 to 60°C / min under a pressure of 5 to 20MPa for β-crystallization reaction, and then cooling to room temperature to obtain a low melt index and low shrinkage PPH sheet. The organic-inorganic composite β-nucleating agent-reinforced particles are obtained by cross-linking an acid-terminated prepolymer obtained by a catalytic reaction of diamino-terminated polydimethylsiloxane and a dibasic acid through an amino-modified inorganic nucleating agent. The PPH sheet of the present invention can significantly enhance its acid and alkali resistance and physical properties by using specific organic-inorganic composite β-nucleating agent-reinforced particles for β-crystallization reaction and enhanced modification.

Description

Technical Field

[0001] The invention belongs to the technical field of functional high molecular polymer materials, and in particular relates to a low melt index and low shrinkage PPH sheet and a preparation method thereof. Background Art

[0002] The research on high performance of general polymer materials has become the main research direction of polymer material development, and the application field of general polymer materials has been continuously expanded. Polyolefin resin is the fastest growing general polymer material product. Especially polypropylene (PP). PP has many excellent properties such as light weight, good heat resistance, high hardness, and easy processing. It is not only widely used in textile fibers, household daily necessities, construction, and automobile industries, but also has a wide range of applications in medical and health, biology and other fields. Although PP has many advantages, there are still some shortcomings, which also limits its application in a wider range of fields. The biggest disadvantage of PP is its poor impact resistance at room temperature and low temperature, so how to obtain high-toughness polypropylene materials is one of the important topics for modifying polypropylene. At present, the toughening modification of PP is mainly divided into chemical toughening modification and physical toughening modification.

[0003] The chemical toughening modification method mainly introduces some highly elastic segments into the isotactic polypropylene chain, mainly including copolymerization modification, grafting modification and the use of metallocene catalysts to regulate the molecular structure. However, the chemical toughening modification method has the defects of insufficient flexibility in adjusting product performance and high cost. In addition, chemical toughening modification leads to a decrease in the isotacticity of the molecular chain and an increase in the degree of randomness. At this time, the flexibility of the molecular chain increases. Compared with homopolymer polypropylene, although the toughness is improved, the material stiffness is reduced, and the melt index and shrinkage rate are increased, which affects its application performance and processing stability.

[0004] The main methods of physical toughening modification of PP include blending toughening, inorganic rigid particle toughening and β-crystal nucleating agent toughening. PP blending toughening method is widely used due to its significant effect, low industrial investment and rapid and easy implementation. Blending toughening of rubber or thermoplastic elastomer with PP is a method that has been studied more and has the most obvious toughening effect.

[0005] β-crystal nucleating agent toughening modification is also a toughening technology developed in recent years. The advantage of this technology is that it basically maintains rigidity while improving the toughness and heat deformation temperature of polypropylene materials. For example, PPH (alloy polypropylene) is a type of homopolymer polypropylene that is β-modified from ordinary PP materials. It has a uniform and delicate Beta crystal structure, excellent chemical corrosion resistance, wear resistance, good insulation, high temperature resistance, and an operating temperature of up to 100°C. It is non-toxic, light in weight, and easy to transport and install. It is a product with better high temperature resistance, corrosion resistance, and aging resistance than ordinary PP materials.

[0006] As described in CN101896518B, a heterophasic propylene copolymer with improved creep behavior is provided, which uses a propylene homopolymer (PPH) and 12.0 wt% to 18.0 wt% of ethylene propylene rubber (EPR), and provides a heterophasic propylene copolymer with improved balance between rigidity and impact strength. That is, rubber blending toughening and β-crystal modification are simultaneously used. However, simple EPR toughening and β-crystal modification have very limited effect on improving the strength and shrinkage properties of the material. Summary of the invention

[0007] In view of the shortcomings and deficiencies of the above prior art, the primary purpose of the present invention is to provide a method for preparing a low melt index and low shrinkage PPH sheet. The PPH sheet of the present invention uses a specific organic-inorganic composite β-nucleating agent to enhance the particles for β-crystallization reaction and enhanced modification, thereby improving its toughness without reducing the strength, stiffness and processing stability of the material.

[0008] Another object of the present invention is to provide a low melt index and low shrinkage PPH sheet prepared by the above method.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] A method for preparing a low melt index and low shrinkage PPH sheet, comprising the following preparation steps:

[0011] Homopolymerized polypropylene and organic-inorganic composite β-nucleating agent reinforced particles are added into a mixer for melting and blending uniformly, and then extruded into a mold, and rapidly quenched to an isothermal crystallization temperature at a speed of 30-60°C / min under a pressure of 5-20MPa for β-crystallization reaction, and then cooled to room temperature to obtain a low melt index and low shrinkage PPH sheet;

[0012] The organic-inorganic composite β-nucleating agent reinforced particles are prepared by the following method:

[0013] (1) subjecting an inorganic nucleating agent to a surface modification reaction using an aminosilane coupling agent to obtain an amino-modified inorganic nucleating agent;

[0014] (2) adding diamino-terminated polydimethylsiloxane, dibasic acid and catalyst into an organic solvent and dissolving them uniformly, heating to 160-220° C. for heat preservation reaction to obtain an acid-terminated prepolymer; then adding the amino-modified inorganic nucleating agent of step (1) to continue heat preservation cross-linking reaction, drying and granulating after the reaction is completed to obtain organic-inorganic composite β-nucleating agent reinforced particles.

[0015] Preferably, the inorganic nucleating agent in step (1) is calcium silicate, and the steps of the surface modification reaction are as follows:

[0016] Calcium silicate and aminosilane coupling agent KH550 are added to anhydrous ethanol, stirred and mixed evenly, heated to 40-70° C., deionized water is added dropwise for coupling reaction, and the product is filtered, washed and dried to obtain calcium silicate surface-modified with aminosilane coupling agent.

[0017] Preferably, the amount of aminosilane coupling agent KH550 added is 1% to 6% of the mass of calcium silicate.

[0018] Preferably, the bis-amino-terminated polydimethylsiloxane in step (2) is an aminopropyl-terminated polydimethylsiloxane with a molecular weight range of 500 to 3000. Its molecular formula is NH2C3H6-Si(CH3)2-(OSi(CH3)2) n -OSi(CH3)2-C3H6NH2. This raw material has high reaction activity and good copolymerization effect; it also has a wide source and low cost.

[0019] Preferably, the dibasic acid in step (2) is an aliphatic dibasic acid having 3 to 10 carbon atoms, such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid.

[0020] Preferably, the molar ratio of the bisamino-terminated polydimethylsiloxane to the dibasic acid added in step (2) is 1:1.5-2.0.

[0021] Preferably, the catalyst in step (2) is 4-dimethylaminopyridine, and the amount of the catalyst added is 0.05% to 1% of the total mass of the bisamino-terminated polydimethylsiloxane and the dibasic acid.

[0022] Preferably, the organic solvent in step (2) is dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF).

[0023] Preferably, the insulation reaction time in step (2) is 2 to 10 hours; and the acid value of the acid-terminated prepolymer is 10 to 40 mgKOH / g.

[0024] Preferably, the amount of the amino-modified inorganic nucleating agent added in step (2) is 0.5% to 10% of the total mass of the bisamino-terminated polydimethylsiloxane and the dibasic acid.

[0025] Preferably, the heat preservation cross-linking reaction time in step (2) is 2 to 24 hours, and the acid value of the product is 0.5 to 5 mgKOH / g when sampled and tested, indicating that the reaction is complete.

[0026] Preferably, the homopolypropylene has a melt index of 1 to 5 g / 10 min, and an isotactic index of >95%.

[0027] Preferably, the addition amount of the organic-inorganic composite β-nucleating agent reinforcing particles is 0.05% to 0.1% of the mass of the homopolypropylene in terms of the content of the inorganic nucleating agent.

[0028] Preferably, the melt blending temperature is 180-220° C.; the isothermal crystallization temperature is 100-140° C., and the β crystallization reaction time is 15-180 min.

[0029] A PPH sheet with low melt index and low shrinkage is prepared by the method.

[0030] The principle of the present invention is: β-nucleating agents are mainly divided into organic and inorganic types. Organic types mainly include organic dibasic acids and their salts (mainly calcium salts) and amide compounds; inorganic types mainly include calcium salts such as calcium silicate and calcium carbonate. In general, the nucleation efficiency of organic β-nucleating agents is relatively high while that of inorganic types is relatively low. However, the molecular weight of organic β-nucleating agents is generally low, which has an adverse effect on the mechanical properties of polymer polypropylene materials. Inorganic β-nucleating agents have a certain reinforcing effect on the mechanical properties of the material. The organic-inorganic composite β-nucleating agent reinforced particles of the present invention are based on the inorganic nucleating agent calcium silicate as the core. Calcium silicate and silane coupling agent have a strong binding force, so the surface modification of aminosilane coupling agent can be carried out efficiently, so that a large number of active amino groups are distributed on the surface of calcium silicate. Then it is used to cross-link the acid-terminated polyamide prepolymer to form a polyamide cross-linked network with calcium silicate as the core. At the same time, the acid-terminated polyamide prepolymer can also form an organic acid calcium structure with trace free calcium ions in calcium silicate, which also has the effect of inducing the production of β crystals. Through the above combination, the nucleation effect of the β crystallization reaction is significantly enhanced. In addition, by introducing flexible polysiloxane segments and multi-dimensional cross-linked networks, the flexibility and strength of the PPH sheet are significantly enhanced, and its low melt index and low shrinkage characteristics are maintained.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The organic-inorganic composite β nucleating agent reinforced particles of the present invention have the characteristics of inorganic nucleating agents and amide, organic acid and organic acid calcium organic nucleating agents, which can significantly improve the nucleation efficiency of β crystallization reaction and enhance its acid and alkali resistance and physical properties. In addition, the organic component of the nucleating agent has high molecular cross-linking characteristics, which avoids the adverse effects of low molecular organic nucleating agents on the mechanical properties of high molecular polypropylene materials.

[0033] (2) The organic-inorganic composite β-nucleating agent reinforced particles of the present invention use inorganic nucleating agents as one-dimensional crosslinking sites, crosslink two-dimensional polysiloxane polyurethane linear polymers, and finally form a three-dimensional crosslinking network in homopolypropylene. The nucleating agent is evenly distributed, which significantly improves the nucleation effect of the β crystallization reaction; at the same time, the introduced polysiloxane polymer can significantly improve the flexibility of the PPH sheet; in addition, the three-dimensional crosslinking network formed in the homopolypropylene can maintain its strength and rigidity without reduction, and the resulting PPH sheet can maintain the characteristics of low melt index and low shrinkage. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0035] Example 1

[0036] A method for preparing a low melt index and low shrinkage PPH sheet, comprising the following preparation steps:

[0037] (1) Calcium silicate and 2% of the mass of aminosilane coupling agent KH550 of calcium silicate are added to anhydrous ethanol and stirred to mix evenly, heated to 55-60° C., deionized water is added dropwise to carry out coupling reaction for 2 hours, and the amount of deionized water added is 5% of the mass of KH550. The product is filtered, washed with deionized water, and vacuum dried to obtain calcium silicate surface-modified with aminosilane coupling agent.

[0038] (2) Add bisaminopropyl-terminated polydimethylsiloxane with an average molecular weight of 500, succinic acid and catalyst 4-dimethylaminopyridine into DMSO and dissolve evenly. The molar ratio of bisaminopropyl-terminated polydimethylsiloxane to succinic acid is 1:1.5, and the amount of 4-dimethylaminopyridine added is 0.1% of the total mass of bisaminopropyl-terminated polydimethylsiloxane and succinic acid. Then heat to 160-180° C. in an autoclave for 5 hours to obtain an acid-terminated prepolymer. The acid value of the obtained acid-terminated prepolymer is 12.8 mgKOH / g. Then, the calcium silicate surface-modified by the aminosilane coupling agent of step (1) is added and the cross-linking reaction is continued for 6 hours. The amount of calcium silicate surface-modified by the aminosilane coupling agent added is 1% of the total mass of the diaminopropyl-terminated polydimethylsiloxane and succinic acid. The acid value of the product is detected to be 1.07 mgKOH / g. After the reaction is completed, the particles are dried and granulated to obtain organic-inorganic composite β-nucleating agent reinforced particles.

[0039] (3) homopolypropylene (melt index of 3.10 g / 10 min, isotactic index of 96.5%) and the organic-inorganic composite β-nucleating agent reinforced particles of step (2) are added into an internal mixer and melt-blended uniformly at 180-220° C., wherein the amount of the organic-inorganic composite β-nucleating agent reinforced particles added is 0.05% of the mass of the homopolypropylene in terms of calcium silicate content. The homopolypropylene is then extruded into a mold, rapidly quenched to 100-110° C. at a speed of 60° C. / min under a pressure of 10 MPa for β crystallization reaction for 15 min, and then cooled to room temperature to obtain a low melt index and low shrinkage PPH sheet.

[0040] Example 2

[0041] A method for preparing a low melt index and low shrinkage PPH sheet, comprising the following preparation steps:

[0042] (1) Calcium silicate and 4% of the mass of aminosilane coupling agent KH550 of calcium silicate are added to anhydrous ethanol and stirred to mix evenly, heated to 55-60° C., deionized water is added dropwise to carry out coupling reaction for 2 hours, and the amount of deionized water added is 5% of the mass of KH550. The product is filtered, washed with deionized water, and vacuum dried to obtain calcium silicate surface-modified with aminosilane coupling agent.

[0043] (2) Add bisaminopropyl-terminated polydimethylsiloxane with an average molecular weight of 1200, adipic acid and catalyst 4-dimethylaminopyridine into DMSO and dissolve evenly. The molar ratio of bisaminopropyl-terminated polydimethylsiloxane to adipic acid is 1:1.75, and the amount of 4-dimethylaminopyridine added is 0.2% of the total mass of bisaminopropyl-terminated polydimethylsiloxane and adipic acid. Then heat to 180-200° C. in an autoclave for 5 hours to obtain an acid-terminated prepolymer. The acid value of the acid-terminated prepolymer obtained by sampling and testing is 24.5 mgKOH / g. Then, the calcium silicate surface-modified by the aminosilane coupling agent of step (1) is added and the cross-linking reaction is continued for 6 hours. The amount of calcium silicate surface-modified by the aminosilane coupling agent added is 4% of the total mass of the diaminopropyl-terminated polydimethylsiloxane and adipic acid. The acid value of the product is detected to be 1.36 mgKOH / g. After the reaction is completed, the particles are dried and granulated to obtain organic-inorganic composite β-nucleating agent reinforced particles.

[0044] (3) homopolypropylene (melt index of 3.10 g / 10 min, isotactic index of 96.5%) and the organic-inorganic composite β-nucleating agent reinforced particles of step (2) are added into an internal mixer and melt-blended uniformly at 180-220° C., wherein the amount of the organic-inorganic composite β-nucleating agent reinforced particles added is 0.075% of the mass of the homopolypropylene in terms of calcium silicate content. The homopolypropylene is then extruded into a mold, rapidly quenched to 110-120° C. at a speed of 50° C. / min under a pressure of 15 MPa for β crystallization reaction for 30 min, and then cooled to room temperature to obtain a low melt index and low shrinkage PPH sheet.

[0045] Example 3

[0046] A method for preparing a low melt index and low shrinkage PPH sheet, comprising the following preparation steps:

[0047] (1) Calcium silicate and aminosilane coupling agent KH550 accounting for 6% of the mass of calcium silicate are added to anhydrous ethanol and stirred to mix evenly, heated to 55-60° C., deionized water is added dropwise to carry out coupling reaction for 2 hours, and the amount of deionized water added is 5% of the mass of KH550. The product is filtered, washed with deionized water, and vacuum dried to obtain calcium silicate surface-modified with aminosilane coupling agent.

[0048] (2) Add bisaminopropyl-terminated polydimethylsiloxane with an average molecular weight of 2000, suberic acid and catalyst 4-dimethylaminopyridine into DMSO and dissolve evenly. The molar ratio of bisaminopropyl-terminated polydimethylsiloxane to suberic acid is 1:1.9, and the amount of 4-dimethylaminopyridine added is 0.4% of the total mass of bisaminopropyl-terminated polydimethylsiloxane and suberic acid. Then heat to 180-200° C. in an autoclave for 5 hours to obtain an acid-terminated prepolymer. The acid value of the obtained acid-terminated prepolymer is 30.7 mgKOH / g after sampling and testing. Then, the calcium silicate surface-modified by the aminosilane coupling agent of step (1) is added and the cross-linking reaction is continued for 6 hours. The amount of calcium silicate surface-modified by the aminosilane coupling agent added is 8% of the total mass of the bis-aminopropyl-terminated polydimethylsiloxane and suberic acid. The acid value of the product is detected to be 0.84 mgKOH / g. After the reaction is completed, the particles are dried and granulated to obtain organic-inorganic composite β-nucleating agent reinforced particles.

[0049] (3) homopolypropylene (melt index of 3.10 g / 10 min, isotactic index of 96.5%) and the organic-inorganic composite β-nucleating agent reinforced particles of step (2) are added into an internal mixer and melt-blended uniformly at 180-220° C., wherein the amount of the organic-inorganic composite β-nucleating agent reinforced particles added is 0.1% of the mass of the homopolypropylene in terms of calcium silicate content. The homopolypropylene is then extruded into a mold, rapidly quenched to 120-130° C. at a speed of 40° C. / min under a pressure of 20 MPa for β crystallization reaction for 60 min, and then cooled to room temperature to obtain a low melt index and low shrinkage PPH sheet.

[0050] Comparative Example 1

[0051] A method for preparing a PPH sheet includes the following steps:

[0052] Homopolymer polypropylene (melt index of 3.10 g / 10 min, isotactic index of 96.5%) and calcium silicate, a β-nucleating agent, are added to an internal mixer and melt-blended uniformly at 180-220°C, with the addition amount of calcium silicate being 0.1% of the mass of homopolymer polypropylene. The product is then extruded into a mold, rapidly quenched to 120-130°C at a speed of 40°C / min under a pressure of 20 MPa for β crystallization reaction for 60 min, and then cooled to room temperature to obtain a PPH sheet.

[0053] The properties of the PPH sheets and homopolypropylene (PP) raw materials obtained in the above Examples 1 to 3 and Comparative Example 1 were tested, and the results are shown in Table 1 below.

[0054] Table 1

[0055]

[0056] It can be seen from the results in Table 1 that the present invention can significantly improve the strength and toughness of the PPH sheet by adding organic-inorganic composite β-nucleating agent to strengthen the particles and perform β-crystallization reaction, and has low melt index and low shrinkage characteristics. Compared with a simple inorganic β-nucleating agent, its effect of improving toughness is more significant, and it can significantly improve the strength of the PPH sheet and reduce its melt index and shrinkage.

[0057] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a low melt index and low shrinkage PPH sheet, characterized in that: The method comprises the following preparation steps: Homopolymer polypropylene and organic-inorganic composite β-nucleating agent reinforced particles are added into a mixer for melting and blending, and then extruded into a mold, and rapidly quenched to an isothermal crystallization temperature at a speed of 30-60°C / min under a pressure of 5-20MPa for β-crystallization reaction, and then cooled to room temperature to obtain a low melt index and low shrinkage PPH sheet; The organic-inorganic composite β-nucleating agent reinforced particles are prepared by the following method: (1) using an aminosilane coupling agent to carry out a surface modification reaction on an inorganic nucleating agent to obtain an amino-modified inorganic nucleating agent; (2) adding diamino-terminated polydimethylsiloxane, dibasic acid and catalyst into an organic solvent and dissolving them uniformly, heating to 160-220° C. for heat preservation reaction to obtain an acid-terminated prepolymer; then adding the amino-modified inorganic nucleating agent of step (1) to continue heat preservation cross-linking reaction, drying and granulating after the reaction is completed to obtain organic-inorganic composite β-nucleating agent reinforced particles; The dibasic acid is an aliphatic dibasic acid having 3 to 10 carbon atoms; the molar ratio of the bisamino-terminated polydimethylsiloxane to the dibasic acid is 1:1.5 to 2.

0.

2. The method for preparing a low melt index and low shrinkage PPH sheet according to claim 1, characterized in that: The inorganic nucleating agent in step (1) is calcium silicate, and the steps of the surface modification reaction are as follows: Calcium silicate and aminosilane coupling agent KH550 are added to anhydrous ethanol, stirred and mixed evenly, heated to 40-70° C., deionized water is added dropwise for coupling reaction, and the product is filtered, washed and dried to obtain aminosilane coupling agent surface-modified calcium silicate; the amount of aminosilane coupling agent KH550 added is 1%-6% of the mass of calcium silicate.

3. The method for preparing a low melt index and low shrinkage PPH sheet according to claim 1, characterized in that: The bis-amino-terminated polydimethylsiloxane in step (2) is an aminopropyl-terminated polydimethylsiloxane with a molecular weight ranging from 500 to 3000.

4. The method for preparing a low melt index and low shrinkage PPH sheet according to claim 1, characterized in that: The catalyst in step (2) is 4-dimethylaminopyridine, and the amount of the catalyst added is 0.05% to 1% of the total mass of the bisamino-terminated polydimethylsiloxane and the dibasic acid.

5. The method for preparing a low melt index and low shrinkage PPH sheet according to claim 1, characterized in that: The organic solvent in step (2) is DMSO or DMF; the insulation reaction time is 2 to 10 hours; and the acid value of the acid-terminated prepolymer is 10 to 40 mgKOH / g.

6. The method for preparing a low melt index and low shrinkage PPH sheet according to claim 1, characterized in that: The amount of the amino-modified inorganic nucleating agent added in step (2) is 0.5% to 10% of the total mass of the bis-amino-terminated polydimethylsiloxane and the dibasic acid.

7. The method for preparing a low melt index and low shrinkage PPH sheet according to claim 1, characterized in that: The heat preservation cross-linking reaction time in step (2) is 2 to 24 hours, and the acid value of the product is 0.5 to 5 mgKOH / g after sampling and detection, indicating that the reaction is complete.

8. The method for preparing a low melt index and low shrinkage PPH sheet according to claim 1, characterized in that: The homopolypropylene has a melt index of 1-5 g / 10 min and an isotactic index of >95%. The amount of the organic-inorganic composite β-nucleating agent reinforcing particles added is 0.05%-0.1% of the mass of the homopolypropylene based on the content of the inorganic nucleating agent.

9. The method for preparing a low melt index and low shrinkage PPH sheet according to claim 1, characterized in that: The temperature of the melt blending is 180-220° C.; the isothermal crystallization temperature is 100-140° C., and the time of the β crystallization reaction is 15-180 min.

10. A low melt index and low shrinkage PPH sheet, characterized in that: It is prepared by the method according to any one of claims 1 to 9.

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