Hydrolysis-resistant thermoplastic elastomer compound as well as preparation method and application thereof

Abstract

The invention discloses a hydrolysis-resistant thermoplastic elastomer compound as well as a preparation method and application thereof, and relates to the technical field of high polymer materials. The hydrolysis-resistant thermoplastic elastomer compound comprises the following components in parts by weight: 20-31 parts of a styrene elastomer, 3-15 parts of a compatilizer, 20-60 parts of a rubber plasticizer, 30-45 parts of elastomer resin and 0.02-0.8 part of an antioxidant, the weight-average molecular weight of the styrene elastomer is greater than or equal to 160000, and the Noacrylic value of the rubber plasticizer is less than or equal to 8%. According to the hydrolysis-resistant thermoplastic elastomer compound disclosed by the invention, the hydrolysis resistance of the thermoplastic elastomer compound is effectively improved through the synergistic effect of all the components, and the hydrolysis-resistant thermoplastic elastomer compound is a food-grade Tritan-encapsulated thermoplastic elastomer compound and can generate strong adhesion with Tritan.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and more specifically to a hydrolysis-resistant thermoplastic elastomer composite, a preparation method and application thereof. Background Art

[0002] PCTG is a transparent plastic obtained by copolymerization of terephthalic acid, tetramethylcyclobutanediol, 1,4-cyclohexanedimethanol and ethylene glycol. Tritan produced by Eastman Company in the United States has the advantages of being clear and transparent, free of bisphenol A, excellent in high temperature resistance, excellent in impact resistance, etc. It has passed the US FDA certification and is widely used in tableware such as baby bottles, water cups, and soup spoons. Thermoplastic elastomers (TPE-S (Thermoplastic elastomer-Styrenic)) are often used for secondary encapsulation molding with other hard plastics, which can provide a soft touch and increase the friction coefficient to prevent slipping. When used as a sealing gasket, it can also block the outside air. However, thermoplastic elastomers currently have defects such as poor hydrolysis resistance and weak adhesion with Tritan. How to meet the EU's food-grade contact requirements is also a performance that needs to be improved urgently.

[0003] The prior art discloses a coating material for PCTG plastics, which includes the following raw materials by weight: 20-30 parts of SEBS, 10-15 parts of SBS, 20-45 parts of mineral oil, 15-25 parts of wollastonite, 15-35 parts of polyurethane elastomer, 3-19 parts of tannic acid, 15-23 parts of carrageenan, 9-33 parts of citric acid, 5-10 parts of TPU / SEBS, 1-3 parts of masterbatch, 0.5-1.5 parts of antioxidant and 0.5-1.5 parts of surface treatment agent. Although the prior art improves the bonding strength of TPE coating material and PCTG plastics, the hydrolysis resistance of TPU itself is poor and cannot meet the food grade contact requirements of the EU. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects and shortcomings of the existing encapsulation materials for PCTG plastics, such as poor hydrolysis resistance and inability to meet the food-grade contact requirements of the European Union, and to provide a hydrolysis-resistant thermoplastic elastomer composite, which effectively improves the hydrolysis resistance of the thermoplastic elastomer composite through the synergistic effect of various components, has a low migration amount, is a food-grade encapsulated Tritan thermoplastic elastomer composite, and can produce strong adhesion with Tritan.

[0005] Another object of the present invention is to provide a method for preparing a hydrolysis-resistant thermoplastic elastomer compound.

[0006] Another object of the present invention is to provide a hydrolysis-resistant thermoplastic elastomer compound for use in encapsulation of copolyester products.

[0007] Another object of the present invention is to provide a copolyester food-grade product.

[0008] The above object of the present invention is achieved by the following technical solutions:

[0009] A hydrolysis-resistant thermoplastic elastomer composite, in parts by weight, comprises the following components:

[0010] 20-31 parts of a styrenic elastomer, 3-15 parts of a compatibilizer, 20-60 parts of a rubber plasticizer, 30-45 parts of a polyether-based polyurethane, and 0.02-0.8 parts of an antioxidant.

[0011] The weight-average molecular weight of the styrenic elastomer is ≥160,000.

[0012] The Noack value of the rubber plasticizer is ≤8%.

[0013] In the hydrolysis-resistant thermoplastic elastomer composite of the present invention, the weight ratio of the styrenic elastomer to the total weight of the hydrolysis-resistant thermoplastic elastomer composite is greater than or equal to 15%, preferably 19-25% of the total weight of the hydrolysis-resistant thermoplastic elastomer composite, such as 19%, 20%, 21%, 22%, 23%, 24%, 25%, etc.

[0014] Among them, it should be noted that:

[0015] The Noack value of the rubber plasticizer of the present invention is measured by the standard method of ASTM D6375-09-2019.

[0016] The weight-average molecular weight of the styrenic elastomer of the present invention is measured by liquid chromatography, referring to the standard method of GB / T21864-2008 for measurement:

[0017] Preferably, the hydrolysis-resistant thermoplastic elastomer composite, in parts by weight:

[0018] 22 parts of a styrenic elastomer, 12 parts of a compatibilizer, 30 parts of a rubber plasticizer, 32 parts of a polyether-based polyurethane, and 0.1 part of an antioxidant;

[0019] Or 25 parts of a styrenic elastomer, 10 parts of a compatibilizer, 35 parts of a rubber plasticizer, 34 parts of a polyether-based polyurethane, and 0.3 part of an antioxidant;

[0020] Or 27 parts of a styrenic elastomer, 8 parts of a compatibilizer, 40 parts of a rubber plasticizer, 38 parts of a polyether-based polyurethane, and 0.5 part of an antioxidant;

[0021] Or 30 parts of a styrenic elastomer, 4 parts of a compatibilizer, 50 parts of a rubber plasticizer, 42 parts of a polyether-based polyurethane, and 0.8 part of an antioxidant, etc.

[0022] The hydrolysis-resistant thermoplastic elastomer composite of the present invention uses polyether-type polyurethane as the thermoplastic elastomer. The polyether bond structure is more stable, and compared with the elastomer resin, the overall thermoplastic elastomer composite can have more stable hydrolysis resistance. And because copolyesters such as PCTG have strong polarity, through the synergistic effect of the compatibilizer and styrenic elastomer in the present invention, the self-polarity of the thermoplastic elastomer composite is significantly improved, thereby enhancing the encapsulation force between the thermoplastic elastomer composite and the copolyester.

[0023] In the hydrolysis-resistant thermoplastic elastomer composite of the present invention, by controlling the Noack value of the rubber plasticizer and the weight-average molecular weight of the styrenic elastomer, the migration amount of the hydrolysis-resistant thermoplastic elastomer composite can be significantly reduced through their synergistic effect, and the migration amount in solutions such as acetic acid ethanol can be reduced, meeting the requirements of EU food contact (EU) No10 / 2011.

[0024] Preferably, the weight of the polyether-type polyurethane is 25-38% of the weight of the hydrolysis-resistant thermoplastic elastomer composite.

[0025] In the hydrolysis-resistant thermoplastic elastomer composite of the present invention, by optimizing the addition ratio of the polyether-type polyurethane, on the one hand, the proportion of polar components can be increased to generate stronger adhesion with copolyesters such as PCTG, and on the other hand, the material hardness of the thermoplastic elastomer composite can be controlled and optimized, improving the feel of the thermoplastic elastomer composite material, enhancing the material cooling rate, and being more conducive to processing and forming in actual production.

[0026] The ratio of the hard segment to the soft segment of the polyether-type polyurethane in the present invention is 2-3:1.

[0027] Preferably, the weight-average molecular weight of the styrenic elastomer is 180,000-240,000, and can be, for example, 180,000, 190,000, 200,000, 210,000, 220,000, 230,000, 240,000, etc.

[0028] Preferably, the Noack value of the rubber plasticizer is 6-3%, and can be, for example, 3%, 4%, 5% or 6%, etc.

[0029] In the hydrolysis-resistant thermoplastic elastomer composite of the present invention, the following components can all be conventional types in the art. The following only lists the components that can be used in the specific embodiments, and does not make specific limitations.

[0030] In the specific embodiment, the compatibilizer of the present invention can be at least one of ethylene-vinyl acetate resin, petroleum resin, acrylic copolymer, hydrogenated styrene-isoprene and maleic anhydride grafted SEBS.

[0031] More preferably, it is maleic anhydride grafted SEBS, which is more conducive to enhancing the encapsulation strength.

[0032] In a specific embodiment, the plasticizer of the present invention may be silicone oil, paraffin oil, naphthenic oil, etc.

[0033] In a specific embodiment, the styrenic elastomer of the present invention may be at least one of styrene-ethylene-butene-styrene block copolymer and styrene-ethylene-ethylene-propylene-styrene copolymer.

[0034] The mass percentage of styrene in the styrenic elastomer of the present invention is 28-35%, and may be, for example, 28%, 29%, 30%, 31%, 32%, 33%, 34% or 35%.

[0035] Among them, the mass percentage of styrene in the styrenic elastomer is measured according to the standard method ASTM D5775-2014.

[0036] In a specific embodiment, the antioxidant of the present invention may be one or several of antioxidant 264, antioxidant 412S, antioxidant 1010, antioxidant 1076, antioxidant 1790, antioxidant 168 or antioxidant 626.

[0037] The present invention also specifically protects a method for preparing a hydrolysis-resistant thermoplastic elastomer composite, comprising the following steps:

[0038] Mix the components evenly, add them into a twin-screw extruder, the extrusion temperature is 130°C - 210°C, and after extrusion, plasticization, cooling and pelletizing, a hydrolysis-resistant thermoplastic elastomer composite is obtained.

[0039] Among them, the twin-screw extruder of the present invention may preferably be a twin-screw extruder with a length-to-diameter ratio of not less than 56:1, the rotation speed of the twin-screw extruder is 300 - 600 revolutions per minute, and the total feeding speed is 150 - 300 kg / h.

[0040] The present invention also specifically protects the application of a hydrolysis-resistant thermoplastic elastomer composite in encapsulating copolyester products.

[0041] The hydrolysis-resistant thermoplastic elastomer composite of the present invention can be used to encapsulate various copolyester products, such as PCTG products.

[0042] The present invention also specifically protects a copolyester food-grade product, which is prepared by encapsulating a copolyester product with a hydrolysis-resistant thermoplastic elastomer composite.

[0043] The hydrolysis-resistant thermoplastic elastomer composite of the present invention is easy to be injection-molded, hydrolysis-resistant, can meet the requirements of EU food-grade contact (EU) No 10 / 2011, can generate strong adhesion with copolyesters such as Tritan, and can be widely used in food-contact copolyester food-grade products that are repeatedly washed and used, such as: encapsulating drinking water cups, food box seals, etc.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] The hydrolysis-resistant thermoplastic elastomer composite of the present invention effectively improves the hydrolysis resistance of the thermoplastic elastomer composite through the synergistic effect of each component, is a thermoplastic elastomer composite for food-grade overmolding Tritan, and can produce strong adhesion with Tritan. Specific Embodiments

[0046] The present invention will be further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw material reagents used in the embodiments of the present invention are conventional raw material reagents purchased.

[0047] Raw Material Description:

[0048] Styrenic elastomer component:

[0049] A1 Styrene-ethylene-butene-styrene block copolymer, weight average molecular weight 160,000, Taipol 6154, Formosa Plastics;

[0050] A2 Styrene-ethylene-butene-styrene block copolymer, weight average molecular weight 220,000, Globalprene 7551, LCY;

[0051] A3 Styrene-ethylene-ethylene-propylene-styrene copolymer, weight average molecular weight 250,000, Septon 4055, Kuraray

[0052] A4 Styrene-ethylene-butene-styrene block copolymer, weight average molecular weight 140,000, YH-502T, Yueyang Petrochemical;

[0053] Compatibilizer component (B):

[0054] B1 Maleic anhydride grafted SEBS, Taipol 7131, Formosa Plastics;

[0055] B2 Petroleum resin, Kristalex 5140, Eastman;

[0056] B3 Ethylene-vinyl acetate resin, 7350M, Formosa Plastics;

[0057] Rubber plasticizer (C):

[0058] C1 Paraffin oil, Noack value 5.3%, Pionier 2071P, H&S Germany

[0059] C2 Paraffin oil, Noack value 3.7%, PW-90, Idemitsu Japan

[0060] C3 Paraffin oil, Noack value 10.5%, 500N, Formosa Plastics

[0061] Elastomer resin (D):

[0062] D1: polyether polyurethane, HF-S4080A, Huafeng;

[0063] D2: polyether polyurethane, M90, Meirui New Materials;

[0064] D3: Polyester polyurethane, E265, Meirui New Materials;

[0065] D4: thermoplastic polyester elastomer, KYLflex L3020, KYLflex;

[0066] D5: Ethylene-propylene elastomer resin, Vistamaxx 6202, ExxonMobil.

[0067] Antioxidant (E):

[0068] Irganox 1010, BASF.

[0069] Examples 1 to 9

[0070] A hydrolysis-resistant thermoplastic elastomer composite comprises the following components in parts by weight:

[0071] Table 1

[0072]

[0073]

[0074] The preparation method of the hydrolysis-resistant thermoplastic elastomer composite of the above-mentioned embodiments 1 to 9 is as follows:

[0075] Each component is added in a high-speed stirring device according to the required proportion and mixed evenly;

[0076] The mixed materials are added into a twin-screw extruder with a length-to-diameter ratio of not less than 56:1 by means of a solid-type weight loss meter;

[0077] The speed of the twin-screw extruder was 500 rpm, the total feed to the metering scale was 200 kg / h, and the extruder temperature was set at 180 °C;

[0078] The material is plasticized by the extruder, cooled in a water tank, and then drawn to a pelletizer for pelletizing to obtain a hydrolysis-resistant thermoplastic elastomer compound.

[0079] Comparative Examples 1 to 7

[0080] A thermoplastic elastomer compound comprises the following components in parts by weight:

[0081] Table 2

[0082]

[0083] Result detection

[0084] Perform relevant performance tests on the thermoplastic elastomer composites of the above examples and comparative examples. The specific test methods are as follows:

[0085] Hardness test method:

[0086] Refer to ISO 868:2003 and use a Shore A durometer to measure a 6-mm-thick thermoplastic elastomer sample block.

[0087] Evaluation method for the adhesion to overmolded Tritan:

[0088] First, make a 150*40*2-mm long strip plate of Tritan material, grade TX1001, by injection molding. Then, place the long strip plate into a specific overmolding mold, and bond the materials prepared in the examples and comparative examples to the long strip plate by injection molding to obtain an overmolded strip. The injection molding temperature is 250°C.

[0089] Refer to the VDI 2019 test method, use a universal testing machine, and use a fixture to peel the elastomer material from the overmolded strip at a speed of 200 mm / min, and record the maximum peel force.

[0090] Evaluation method for food grade:

[0091] Cut a 10-cm * 10-cm * 2-cm thermoplastic elastomer sheet, and according to the requirements of (EU) No 10 / 2011, use food simulants A, B, C, and D1, namely 10% ethanol, 3% acetic acid, 20% ethanol, and 50% ethanol, to simulate the overall migration of the elastomer material in aqueous foods, acidic foods, and alcoholic foods, with the requirement being less than 10 mg / dm 2 .

[0092] Evaluation method for hydrolysis resistance:

[0093] Place the injection-molded specimen conforming to ISO 37:2017 in a condition of 85°C and 85% humidity for 7 days, and according to the test method of ISO37, compare the retention rates of the tensile strength and elongation at break after aging.

[0094] The specific test results are shown in Table 3:

[0095] Table 3

[0096]

[0097]

[0098] As can be seen from the above test results of 3, the hydrolysis-resistant thermoplastic elastomer composite of the present invention has good hydrolysis resistance. The retention rate of tensile strength after aging can reach 80-93%, and the retention rate of elongation at break can reach 76-94%. Moreover, the migration amounts of the hydrolysis-resistant thermoplastic elastomer composite of the present invention in ethanol and acetic acid are low, both controlled within 10 mg / dm 2 as follows, and it can meet the food-grade standard. In terms of the adhesion performance to the overmolded Tritan, the hydrolysis-resistant thermoplastic elastomer composite of the present invention also exhibits good adhesion performance, and the overmolding force can reach 4.7-6.9 N / mm.

[0099] Among them, compared with Example 1, the styrenic elastomer component A2 in Example 2 is a preferred styrenic elastomer. After aging at 85°C and 85% humidity for 7 days, the retention rate of tensile strength can reach 91%, the retention rate of elongation at break can reach 88%, and the overmolding force can reach 5.6 N / mm.

[0100] Among them, compared with Examples 4-6, Example 1 uses the preferred compatibilizer component B1 and the preferred rubber plasticizer C1, and its migration amount is significantly reduced. The migration amount in 20% ethanol is only 3.2 mg / dm 2 , and the migration amount in 50% ethanol is only 6.2 mg / dm 2 , and the hydrolysis resistance is also improved.

[0101] Among them, in Comparative Examples 1 and 2, the addition ratio of the elastomer resin is too high or too low, and the precipitation amount is too high. The migration amount in 50% ethanol is greater than 10 mg / dm 2 , and the overmolding force is also reduced to 3.1 N / mm, and the corresponding overmolding Tritan bonding effect cannot be achieved.

[0102] Comparative Examples 3-5 are that the elastomer resin is not within the protection scope of the present invention. The migration amount of Comparative Example 3 seriously exceeds the standard. The migration amount in 10% ethanol is 36.2 mg / dm 2 , the migration amount in 20% ethanol is 48.4 mg / dm 2 , the migration amount in 50% ethanol is 106.8 mg / dm 2 , the overmolding force is also reduced to 2.1 N / mm, and the hydrolysis resistance is also insufficient, and the technical effect of the present invention cannot be achieved at all. The hydrolysis resistance of Comparative Example 4 is also poor, and the overmolding force of Comparative Example 5 is significantly deteriorated, only 0.1 N / mm, and neither can achieve the technical effect of the present invention.

[0103] Comparative Example 6 is that the rubber plasticizer is not within the protection scope of the present invention, and the migration amount seriously exceeds the standard. The migration amount in 10% ethanol is 29.1 mg / dm 2 , the migration amount in 20% ethanol is 40.9 mg / dm 2, the migration amount of 50% ethanol is 83.2 mg / dm 2 .

[0104] Comparative Example 7 is that the styrene-based elastomer is not within the protection scope of the present invention, and the migration amount of 50% ethanol is 20.9 mg / dm 2 , and the food-grade requirements cannot be met.

[0105] Obviously, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made on the basis of the above description. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A hydrolysis-resistant thermoplastic elastomer composite, characterized in that, Comprising the following components in parts by weight: 20 - 31 parts of styrenic elastomer, 3 - 15 parts of compatibilizer, 20 - 60 parts of rubber plasticizer, 30 - 45 parts of polyether-type polyurethane, 0.02 - 0.8 parts of antioxidant, The weight-average molecular weight of the styrenic elastomer is ≥160,000, The Noack value of the rubber plasticizer is ≤8%, 2. The hydrolytically resistant thermoplastic elastomer composite according to claim 1, wherein The weight of the polyether-type polyurethane is 25 - 38% of the weight of the hydrolysis-resistant thermoplastic elastomer composite, 3. The hydrolysis-resistant thermoplastic elastomer composite according to claim 1, wherein The weight-average molecular weight of the styrenic elastomer is 180,000 - 240,000, 4. The hydrolysis-resistant thermoplastic elastomer composite according to claim 1, characterized in that, The Noack value of the rubber plasticizer is 6 - 3%, 5. The hydrolytically resistant thermoplastic elastomer composite according to claim 1, characterized in that, The compatibilizer is at least one of ethylene-vinyl acetate resin, petroleum resin, acrylic copolymer, hydrogenated styrene-isoprene, and maleic anhydride-grafted SEBS, 6. The hydrolysis-resistant thermoplastic elastomer composite according to claim 3, wherein The compatibilizer is maleic anhydride-grafted SEBS, 7. The hydrolysis-resistant thermoplastic elastomer composite according to claim 1, wherein The styrenic elastomer is at least one of styrene-ethylene-butene-styrene block copolymer and styrene-ethylene-ethylene-propylene-styrene copolymer, 8. A method for preparing the hydrolysis-resistant thermoplastic elastomer composite according to any one of claims 1 to 6, characterized in that, Comprising the following steps: Mix the components evenly, add them into a twin-screw extruder, the extrusion temperature is 130°C - 210°C, extrude, plasticize, cool, and pelletize to obtain the hydrolysis-resistant thermoplastic elastomer composite, 9. Use of the hydrolysis-resistant thermoplastic elastomer composite according to claims 1 - 6 in encapsulating copolyester products, 10. A copolyester food-grade product, characterized in that, Prepared by encapsulating copolyester products with the hydrolysis-resistant thermoplastic elastomer composite according to claims 1 - 6

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