CN1508170A - Process for the preparation of thermoplastic vulcanizates - Google Patents

Abstract

The preparation method of thermoplastic vulcanizate of the present invention relates to a method for preparing thermoplastic vulcanizate by dynamic full vulcanization technology, and proposes a new preparation method based on the existing formula for preparing thermoplastic vulcanizate by melt blending method. The operation steps are as follows: (1) premixing of rubber and plastic: first premixing part of rubber and plastic, the total amount of rubber participating in the premixing accounts for 20-60% of the total weight of rubber in the thermoplastic elastomer to be prepared; (2) Preparation of rubber masterbatch: mix the remaining rubber and filler, softener, aging agent and processing aid into masterbatch; (3) dynamic vulcanization: mix the rubber and plastic and plastic premixes prepared in the previous two steps with Dynamic vulcanization of rubber masterbatch, vulcanizing agent and accelerator; (4) late oil filling: add 10-40% oil of plastic weight content, continue to mix evenly, that is, high fluidity, low compression deformation, low hardness physical and mechanical Good performance thermoplastic vulcanizate.

Description

Process for the preparation of thermoplastic vulcanizates

Technical field The present invention relates to a method for preparing thermoplastic vulcanizate by dynamic full vulcanization technology. A new preparation method is proposed based on the existing formula of thermoplastic vulcanizate prepared by melt blending method. This method can prepare high fluidity and low compression deformation , Low hardness thermoplastic vulcanizate.

Background technology The dynamic full vulcanization technology is to mix rubber into the thermoplastic resin matrix, and at the same time of mixing with the cross-linking agent, it can completely produce chemical cross-linking of the rubber "in situ", and under the action of high-speed mixing and shearing, the cross-linking The rubber is crushed into a large number of micron-sized particles, which are dispersed in a continuous thermoplastic resin matrix to form thermoplastic elastic rubber (TPV for short). The rubber that can be selected for preparing TPV usually includes: EPDM rubber, butyl rubber, trans isoprene rubber, natural rubber, butadiene rubber, styrene butadiene rubber, ethylene-vinyl acetate copolymer, acrylate rubber, chlorinated polystyrene Vinyl, Neoprene, Nitrile or mixtures thereof. Thermoplastic resin matrix plastics usually include polypropylene, polyethylene, polystyrene, acrylonitrile-butadiene-styrene terpolymer, styrene-acrylonitrile copolymer, polymethyl methacrylate, polyterephthalic acid Butylene Glycol Esters, Nylon, Polycarbonate or mixtures thereof. Dynamic full vulcanization technology can be used to prepare thermoplastic vulcanizates with a rubber-to-plastic ratio of 90/10 to 10/90. Full vulcanization means that the crosslinking density of the rubber is at least 7×10-5mol/mL or 97% of the rubber is crosslinked. TPV not only has excellent comprehensive performance, but also has the processing characteristics of thermoplastic materials. It is gradually replacing traditional rubber in many fields. The main reason for the rapid development of thermoplastic vulcanizate is that it has the processing and molding advantages of thermoplastics. Compared with rubber, it has higher production efficiency, can be recycled and used repeatedly, and has elastic properties comparable to vulcanized rubber when the temperature requirement is not too high. As early as the early 1980s, there was a typical industrial production of EPDM/PP TPV in foreign countries.

The typical preparation method of TPV is: put the plastic into the high-temperature mixer for pre-melting, then add the rubber together and mix together, then add additives, fillers and softeners in turn to mix evenly, and finally add vulcanizing agent and accelerator for dynamic vulcanization.在“Thermoplastic vulcanizates ofolefin rubber and polyolefin resin”(美国专利US 4130535)、“Thermoplastic elastomeric blends of olefin rubber and polyolefinresin”(美国专利US 4311628)和“Dynamically vulcanized alloyshaving two copolymers in the erosslinked phase and a crystallinematrix”(美国Patent US 5073597) all have reports. Researches in this field at home and abroad basically start from the formulation of raw materials to improve the performance of blended thermoplastics. American Advanced Elastomer Systems Co., Ltd. [AES.Co.] in the "thermoplastic elastomer vulcanizate" (Chinese Patent Application No. 98108434.6) discloses a thermoplastic ternary rubber by dynamic vulcanization in the presence of a vulcanization system. A thermoplastic elastomer vulcanizate prepared from a copolymer, a rubber component and an optional additive, the thermoplastic elastomer vulcanizate has superior physical properties and excellent processability, and the thermoplastic copolymer of the invention has a terpolymer From 10% to 70% by weight of the total composition of at least one thermoplastic terpolymer comprising propylene, ethylene and an alpha-olefin containing at least 4 carbon atoms. The company discloses that the melt flow rate of the polypropylene composition is between about 0.5 and about 5 decigrams in "Polypropylene thermoplastic elastomer composition with high processability and physical performance balance" (Chinese Patent Application No. 99807124.2). /min range, and its molecular weight distribution Mw/Mn is greater than 5.5 to a maximum of about 20, the prepared thermoplastic vulcanizate has improved processability while maintaining excellent physical properties. "Thermoplastic vulcanizates from isobutylene rubber and either EPDM or a conjugated diene rubber" (US Patent No. 5,621,045) discloses a patent application for ternary blending in order to improve the comprehensive performance of TPV. There are two rubber components in the blend, Such as the combination of isobutylene rubber and ethylene propylene rubber or natural rubber, ternary blending is beneficial to improve the overall performance of the blend.

The preparation process of blended thermoplastic vulcanizate is introduced in the review paper "Kinetic Model of Dynamic Vulcanization" (Polym. Mater. sci. Eng 1998, 79 102-103). The preparation process can be roughly classified into two categories. The first category is Melt blending method, this type is also the most common preparation technology currently used in industrial production abroad. This preparation technology mainly has two specific processes. The difference between the two processes lies in the way of adding the vulcanizing agent. One is that the vulcanizing agent is added after the rubber and plastics, fillers and softeners are uniformly mixed, and the other is that the vulcanizing agent is mixed Vulcanizing agents, fillers and softeners are added to the rubber in advance, and then mixed with plastics for dynamic vulcanization. The second type is the solution polymerization method, which is still in the experimental stage.

As we all know, to a certain extent, dynamic vulcanization technology is not very suitable for the preparation of thermoplastic vulcanizates with low hardness and high fluidity, because low hardness TPV is generally obtained by increasing the rubber phase content, a large number of elastomer particles, easy to form a network structure , as the rubber content increases, the elasticity of the material increases, and the prepared material becomes difficult to extrude, or even cannot be extruded. The key to the performance of blended thermoplastic vulcanizates lies in the control methods and means of the morphology structure and the particle size of the rubber phase. Since TPV contains a large number of cross-linked rubber particles, these rubber particles are easy to form a network structure, thereby affecting the fluidity of TPV. If the content of the rubber phase is reduced, the fluidity will increase, but the hardness and compression deformation of TPV will also increase, that is, the elasticity will decrease. Therefore, there is a contradiction between the elasticity and fluidity of TPV, and it has always been a difficult point to prepare TPV with high flow and high elasticity. The traditional approach is generally to solve this problem by changing the formula or adopting more advanced processing equipment.

SUMMARY OF THE INVENTION The present invention aims to propose a method for preparing thermoplastic vulcanizates using conventional thermoplastic vulcanizate formulations in conventional processing equipment. This method can prepare thermoplastic vulcanizates with high fluidity, low compression deformation, and low hardness.

The traditional melt blending method to prepare thermoplastic vulcanizate is to first melt the plastic and mix it with rubber, then add additives, fillers, softeners and mix evenly, and finally add vulcanizing agent and accelerator for dynamic vulcanization. The operation steps of the preparation method proposed by the present invention are as follows:

(1) Premixing of rubber and plastics: first premixing part of rubber and plastics, the total amount of rubber participating in the premixing accounts for 20-60% of the total weight of rubber in the thermoplastic elastomer to be prepared;

(2) Preparation of rubber masterbatch: remaining rubber and filler, softener, aging agent, processing aid are mixed into masterbatch;

(3) Dynamic vulcanization: the rubber-plastic and plastic premix prepared in the last two steps, rubber masterbatch, vulcanizing agent, accelerator are carried out dynamic vulcanization;

(4) Oil filling in the later stage: add 10-40% oil of the weight content of the plastic, and continue to mix evenly to obtain a blended thermoplastic vulcanizate.

The rubber used in the present invention is the commonly used rubber of known thermoplastic vulcanizates, such as: trans isoprene rubber, butadiene rubber, styrene-butadiene rubber, ethylene-vinyl acetate copolymer, acrylate rubber, chlorinated polyethylene rubber, neoprene rubber, nitrile rubber or their mixtures. The used plastics of the present invention are commonly used plastics of known thermoplastic vulcanizates, such as: polystyrene, acrylonitrile-butadiene-styrene terpolymer, styrene-acrylonitrile copolymer, polymethylmethacrylate, Polybutylene terephthalate, nylon, polycarbonate or mixtures thereof.

The oil used for oil extension in the later stage of the present invention is the oil commonly used in known thermoplastic vulcanizates, for example: naphthenic oil, paraffin oil, petrolatum or their mixtures. The type of oil used for post-oil extension is the same as or different from the commonly used softeners for known thermoplastic vulcanizates.

The invention mainly adopts two technologies: one is the premixing of part of rubber and plastic; the other is the technology of filling a certain amount of oil in the late stage of dynamic vulcanization.

The rubber-plastic premixing technology makes the pre-mixing of plastic and part of the rubber very uniform. After further rubber is added, all the rubber and plastic will form a uniform phase in a short time. Because the entire dynamic vulcanization process is very short, this technology can effectively avoid the disadvantages of rubber and plastic that cannot be fully mixed evenly in traditional dynamic vulcanization technology, and also avoids the intentional extension of premixing in some traditional methods to increase the uniformity of rubber and plastic mixing. Time, resulting in the disadvantage of a large amount of migration of fillers and various compounding agents into the plastic phase. The uniform mixing of rubber and plastic is very important for the successful realization of phase inversion in the next step of dynamic vulcanization process and to obtain fine particles uniformly covered by the plastic phase, and fine rubber particles are also necessary for the high fluidity and high elasticity of TPV. prepared.

Post-oil filling technology refers to adding oil equivalent to 20%-40% of the plastic content in the late stage of dynamic vulcanization. This part of oil can be carried out after dynamic vulcanization is completed, or it can be directly oil-filled to the finished TPV. In this way, a small part of the oil energy will penetrate into the rubber particles, and most will remain in the plastic phase. Experiments have proved that as long as the filled oil has sufficient compatibility with plastics and the amount is not too much, it can significantly reduce the hardness and compression deformation of TPV, and can improve fluidity. The reason is to achieve the purpose of reducing the compression set of TPV and improving the fluidity by plasticizing and compatibilizing the molecules of the plastic phase.

The formula used in the present invention is an existing, known thermoplastic vulcanizate formula. On the basis of not changing the original formula and the conventional equipment (open mill, internal mixer or screw extruder) used, a new preparation method is proposed .

Except being existing known commonly used rubber and plastics, other fillers, auxiliary agents are also commonly used, and softening agent is for example: naphthenic oil, paraffin oil or vaseline etc.; Filler is for example: white carbon black, carbon black, silica, Clay, etc.; vulcanizing agents such as: organic peroxides, sulfur, phenolic resins, etc.; other additives such as: stearic acid, antioxidants, etc.

All performance tests of the present invention are all in accordance with the corresponding national standards. From the examples of the present invention and the corresponding comparative examples, it can be clearly seen that the performance of the thermoplastic vulcanizate prepared by the preparation technology of the present invention is the same as that of the thermoplastic vulcanizate prepared by the traditional technology. Compared with that, the thermoplastic elastic rubber prepared by the technology of the present invention is far lower than the vulcanized rubber prepared by the traditional technical method in terms of compression deformation and hardness, other mechanical properties are basically maintained, fluidity can be significantly improved, and compression deformation (reflecting vulcanization The elasticity of the glue) can be reduced by about 8% to 10%, the hardness can be reduced by 5 to 10 Shore degrees, and the mechanical properties can basically be maintained.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is the instron rheological curves of thermoplastic elastic adhesives prepared in Examples and Comparative Examples of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The properties of the thermoplastic elastic adhesives prepared in the examples and comparative examples of the present invention are listed in Table 1.

Example 1 Preparation of butyl rubber/polypropylene (IIR/PP) thermoplastic vulcanizate with a rubber-to-plastic ratio of 60/40 (the rubber involved in premixing accounts for 40% of the total rubber weight, and the later oil extension accounts for 20% of the plastic weight) . The operation steps are as follows:

1) Mix 48 grams of butyl rubber, 80 grams of polypropylene plastic and 0.8 grams of antioxidant 1010 in a double-roller plastic mixer at 170° C. for about 3 minutes, and set aside.

2) Put the remaining 72 grams of butyl rubber into the normal temperature open mill, adjust the appropriate roller distance, and add 1.2 grams of stearic acid and 48 grams of white carbon black in small quantities according to the mixing method of rubber, and beat 6 Add 120 grams of oil (naphthenic oil and petroleum jelly, and use a weight ratio of 1: 1) again, make 6 triangle bags, make rubber masterbatch, and set aside.

3) Put the rubber-plastic premix and rubber masterbatch prepared in the previous two steps into a 180°C double-roller plasticizer in turn, with a roller distance of 0.5mm. After 30 seconds, add 14.2 grams of tert-octyl phenolic resin, mix for 30 seconds, and finally Add 2.8 grams of stannous chloride for dynamic vulcanization for 15 minutes.

4) Add 16 grams of combined oil (naphthenic oil and vaseline, combined with a weight ratio of 1:1), and continue mixing until uniform, that is, an IIR/PP blended thermoplastic vulcanizate with a rubber-to-plastic ratio of 60/40 is obtained. The properties are shown in Table 1 and Figure 1.

Example 2 Preparation of EPDM/PP (EPDM/PP) thermoplastic vulcanizate with a rubber-to-plastic ratio of 80/20 (the rubber involved in premixing accounts for 60% of the total rubber weight, and the late oil-extending accounts for 10% of the plastic weight. %). The operation steps are as follows:

1) Mix 64 grams of EPDM rubber, 40 grams of polypropylene plastic and 0.4 grams of antioxidant 1010 in a mixer at 170°C for about 3 minutes and set aside.

2) Put the remaining 96 grams of EPDM rubber into the open mill at room temperature, adjust the suitable roller distance, and add 1.6 grams of stearic acid and 64 grams of white carbon black in small quantities according to the rubber mixing method. Make 6 triangle bags, then add 160 grams of naphthenic oil, make 6 triangle bags, make rubber masterbatch, set aside.

3) Put the rubber-plastic premix and rubber masterbatch prepared in the previous two steps into a 180°C double-roller plasticizer in turn, with a roller distance of 0.5mm. After 30 seconds, add 4.8 grams of organic peroxide DCP and perform dynamic vulcanization for 8 minutes. .

4) Add 4 grams of naphthenic oil and continue mixing until uniform. That is, an EPDM/PP blended thermoplastic vulcanizate with a rubber-to-plastic ratio of 80/20 was obtained. The properties are shown in Table 1 and Figure 1.

Example 3 Prepare a natural rubber/polyethylene (NR/PE) thermoplastic vulcanizate with a rubber-to-plastic ratio of 70/30 (the rubber involved in premixing accounts for 20% of the total rubber weight, and the oil extension accounts for 40% of the plastic weight in the later stage. The type of oil extension is different from the type of softener in the second step). The operation steps are as follows:

1) Mix 28 grams of natural rubber, 60 grams of polyethylene plastic and 0.6 grams of antioxidant 1010 in a mixer at 170°C for about 3 minutes and set aside;

2) Put the remaining 112 grams of natural rubber into the open mill at room temperature, adjust the appropriate roller distance, and add 1.4 grams of stearic acid and 56 grams of white carbon black in small quantities according to the mixing method of rubber, and beat 6 1 triangular bag, then add 140 grams of paraffin oil, make 6 triangular bags to make rubber masterbatch, set aside;

3) Put the rubber-plastic premix and rubber masterbatch prepared in the previous two steps into a 180°C double-roller plasticizer in turn, with a roller distance of 0.5mm. After 30 seconds, add 14.0 grams of tert-octyl phenolic resin, mix for 30 seconds, and finally Add 2.8 grams of stannous chloride for dynamic vulcanization for 15 minutes;

4) Add 24 grams of combined oil (naphthenic oil and petroleum jelly, combined with a weight ratio of 1:1), and continue mixing until uniform. That is, the NR/PE blended thermoplastic vulcanizate with a rubber-to-plastic ratio of 70/30 was obtained. The properties are shown in Table 1 and Figure 1. It can be seen from the performance table that even if the type of oil extension is changed later, as long as the vulcanized rubber prepared by the technology of the present invention can achieve the purpose of high fluidity, low compression deformation and low hardness.

Comparative Example 1 A IIR/PP thermoplastic vulcanizate with a rubber-to-plastic ratio of 60/40 was prepared using traditional dynamic vulcanization technology (the composition and dosage of the formula are the same as in Example 1). The operation steps are as follows:

1) Put the whole amount of butyl plastic and antioxidant 1010 into a double-drum plastic mixer at 170°C until the plasticization is uniform, about 2 minutes.

2) Then put the whole amount of butyl rubber into the plasticized plastic in the first step, and mix until uniform.

3) When the rubber and plastic in the previous step are mixed evenly, add white carbon black and oil in batches in small quantities. until well mixed. Then adjust the roller distance to 0.5mm, add tert-octyl phenolic resin, mix for 30 seconds, and finally add stannous chloride for dynamic vulcanization for 15 minutes.

The properties are shown in Table 1 and Figure 1. It can be seen from Table 1 and Fig. 1 that the vulcanized rubber prepared by the traditional technology is not as good as the vulcanized rubber prepared by the technology of the present invention in terms of elasticity, fluidity and hardness.

Comparative example 2 Rubber and plastic premixing, no post-filling to prepare IIR/PP thermoplastic vulcanizate with a rubber-plastic ratio of 60/40 (the difference from Example 1 is that after the third step of dynamic vulcanization is completed, no post-filling Oil). The properties are shown in Table 1 and Figure 1. It can be seen from Table 1 and Figure 1 that the implementation of post-oil filling technology can greatly improve the elasticity of vulcanized rubber and reduce the hardness of vulcanized rubber, but reduce the mechanical properties of vulcanized rubber.

Comparative Example 3 Rubber and plastic are not premixed, and IIR/PP thermoplastic vulcanizate with a rubber-plastic ratio of 60/40 is prepared by late-stage oil-extended technology (the ingredients and dosage of the formula are the same as in Example 1). The operation steps are as follows: first use the traditional preparation technology of Comparative Example 1 to carry out dynamic vulcanization, and then use the oil-extending technology of Example 1 to carry out oil-extending in the later stage) The properties are shown in Table 1 and Figure 1. It can be seen from Table 1 and Figure 1 that only the rubber-plastic premixing technology can improve the mechanical properties and elasticity to a certain extent, but cannot reduce the hardness of the vulcanizate.

Comparative Example 4 EPDM/PP thermoplastic vulcanizate with a rubber-to-plastic ratio of 80/20 was prepared by traditional dynamic vulcanization technology (the composition and dosage of the formula are the same as in Example 2, and the preparation technology is the same as in Comparative Example 1). The properties are shown in Table 1 and Figure 1.

Comparative Example 5 NR/PE thermoplastic vulcanizate with a rubber-to-plastic ratio of 80/20 was prepared by traditional dynamic vulcanization technology (the composition and dosage of the formula are the same as in Example 3, and the preparation technology is the same as in Comparative Example 1). The properties are shown in Table 1 and Figure 1.

Table 1 Hardness (Shore A) 100% elongation (MPa) Tensile strength (MPa) Elongation(%) Tear strength (KN/m) Tensile set (%) Compression set (%)100℃×22h Instron rheometer extrusion capillary sample appearance Example 1 65 3.2 11.0 400 33.5 26 35.6 smooth Example 2 49 1.8 7.0 330 20.0 16 23.0 smooth Example 3 55 2.0 9.1 340 26.0 16 25.1 smooth Comparative example 1 71 3.8 10.1 376 28.0 26 45.0 smooth Comparative example 2 70 3.8 11.5 400 32.0 26 40.0 smooth Comparative example 3 65 3.2 9.0 330 29.0 25 38.5 smooth Comparative example 4 54 2.0 7.5 340 20.0 16 32.0 rough Comparative example 5 60 2.5 9.8 380 30.1 20 32.0 smooth

Claims (5)

1. the preparation method of a thermoplastic sulfurized rubber, first with melt-blending process with plastics fusion in advance and rubber mix, add auxiliary agent, filler, tenderizer again and mix, add vulcanizing agent and promotor at last and carry out dynamic vulcanization, it is characterized in that operation steps is as follows:

(1) rubber and plastics premix: earlier with part rubber and plastics premix, the rubber total amount that participates in premix accounts for the 20-60% of rubber gross weight in the thermoplastic elastomer that will prepare;

(2) preparation of rubber rubber master batch: become rubber master batch with remaining rubber and filler, tenderizer, aging agent, processing aid are mixing;

(3) dynamic vulcanization: will go up the rubber and plastic of two step preparations and plastics pre-composition and rubber rubber master batch and vulcanizing agent, promotor and carry out dynamic vulcanization;

(4) later stage is oil-filled: add 10～40% oil of plastics weight content, continue to mix, promptly obtain the blending type thermoplastic cross-linked rubber.

2. the preparation method of thermoplastic sulfurized rubber according to claim 1, it is characterized in that: rubber is trans-isoprene, cis-1,4-polybutadiene rubber, styrene-butadiene rubber(SBR), ethylene-vinyl acetate copolymer, acrylic elastomer, chlorinated polyethylene rubber, chloroprene rubber, paracril or their mixture.

3. the preparation method of thermoplastic sulfurized rubber according to claim 1, it is characterized in that: plastics are polystyrene, acrylonitrile-butadiene-styrene terpolymer, styrene-acrylonitrile copolymer, polymethylmethacrylate, polybutylene terephthalate, nylon, polycarbonate or their mixture.

4. the preparation method of thermoplastic sulfurized rubber according to claim 1, it is characterized in that: the later stage, oil-filled used oil was naphthenic oil, paraffin oil, Vaseline or their mixture.

5. the preparation method of thermoplastic sulfurized rubber according to claim 4, it is characterized in that: the later stage, oil-filled used oil product kind and tenderizer were identical or different.

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