Composite plastic plate for refrigerator liner and preparation method of composite plastic plate

Abstract

The invention relates to the technical field of refrigerators, in particular to a composite plastic plate for a refrigerator inner container and a preparation method of the composite plastic plate, and the refrigerator inner container with modified high-impact polystyrene as a surface layer and a polypropylene-polystyrene alloy material as a bottom layer is prepared through a double-layer extrusion technology. Wherein polypropylene in the polypropylene-polystyrene alloy material is low in polarity and low in solubility with oily substances, so that the refrigerator liner is not easy to crack; the two ends of a modified amino-octa-polyethylene glycol-carboxylic acid molecule in the modified high-impact polystyrene contain active groups which can be crosslinked with groups in the high-impact polystyrene and polyurethane, so that the cohesiveness between the high-impact polystyrene and a polyurethane foaming material can be effectively enhanced, and the problem that the liner of the refrigerator is separated from a shell can be effectively solved. Compared with the prior art, the method has a wide application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of refrigerators, and in particular to a composite plastic plate for a refrigerator liner and a preparation method thereof. Background Art

[0002] With the rapid development of my country's household appliance refrigerator and freezer industry, the refrigerator liner and door lining supporting plastic sheet industry has also developed rapidly. As an important component of refrigerator products, the refrigerator liner accounts for 10.35% of the total weight of the refrigerator, and its carbon emissions account for a large proportion. In addition, the refrigerator liner is formed by melt extrusion and vacuum forming, which has high requirements for the tensile strength and impact strength of the material.

[0003] There are two types of materials for refrigerator liner: one is plastic liner, such as high-impact polystyrene; the other is metal liner, such as aluminum, stainless steel, etc. The advantages of plastic liner are relatively low price, easy processing, light weight, etc., and the disadvantage is poor heat transfer effect; metal liner is just the opposite of plastic liner, its advantage is good heat transfer effect, and the disadvantage is relatively high price, difficult to shape, heavy quality, etc. At present, more than 95% of the refrigerator liner is plastic liner.

[0004] High-impact polystyrene is one of the main raw materials for the current production of refrigerator liners. It has excellent properties such as water resistance and chemical corrosion resistance and is easy to process, but it has low gloss and poor texture. Another main raw material, acrylonitrile-butadiene-styrene copolymer, has high gloss and high-end texture, and good chemical resistance, but these two traditional plastic liners have high carbon emissions and costs.

[0005] For example, patent technical document CN112143153A discloses a refrigerator liner, a refrigerator liner material and a preparation method thereof, wherein the refrigerator liner material is modified high-impact polystyrene, which is then prepared by a twin-screw extruder to obtain the refrigerator liner. The refrigerator liner prepared by the invention has strong impact resistance, but the oil resistance of the high-impact polystyrene material needs to be improved, and the refrigerator liner is prone to cracking during use.

[0006] Polypropylene is an important thermoplastic polymer, which is widely used in the fields of household appliances, mechanical parts, office supplies and communication equipment. It has the advantages of light weight, non-toxicity, odorlessness, good chemical stability, excellent electrical properties, insoluble in general solvents at room temperature, and low water absorption. However, due to the disadvantages of large molding shrinkage and easy shrinkage and deformation, polypropylene is often modified in practical applications. For example, the patent technical document CN103497421A discloses a polypropylene and polystyrene alloy material, which is composed of 40%-50% polypropylene, 35%-45% polystyrene, 10%-15% compound compatibilizer, 0.1%-1% antioxidant, and 0.1%-1% lubricant; the polypropylene in the invention has low polarity and has stronger oil resistance than high-impact polystyrene liner, which has a great improvement on the cracking of the refrigerator liner during use, but has low adhesion to polyurethane foam material, and the liner is prone to shell separation.

[0007] Therefore, according to the above-mentioned related technologies, it is urgent to develop a composite plastic plate for refrigerator liner and a preparation method thereof. Summary of the invention

[0008] In view of this, the purpose of the present invention is to provide a composite plastic plate for a refrigerator liner and a preparation method thereof, so as to solve the problems of liner cracking and liner separation in the prior art.

[0009] Based on the above purpose, the present invention provides a composite plastic plate for a refrigerator liner and a preparation method thereof.

[0010] A composite plastic plate for a refrigerator liner, the composite plastic plate comprising a surface layer and a bottom layer;

[0011] The surface layer is an auxiliary material, and the bottom layer is a main material;

[0012] The auxiliary material is modified high-impact polystyrene;

[0013] The main material is polypropylene-polystyrene alloy material;

[0014] The mass ratio of the modified high-impact polystyrene to the polypropylene-polystyrene alloy material is 4-8:92-96;

[0015] The modified high-impact polystyrene is prepared from the following raw materials in parts by weight:

[0016] High impact polystyrene resin 75-82 parts, polypropylene 6-10 parts, toughening masterbatch 2-3 parts, compatibilizer A 5-8 parts, tackifier 0.3-0.8 parts;

[0017] The polypropylene-polystyrene alloy material is prepared from the following raw materials in parts by weight:

[0018] Polypropylene 20-30 parts, polystyrene 65-75 parts, polyethylene 5-10 parts, compatibilizer B 8-12 parts, toughening agent 3-7 parts, antioxidant 2-3 parts, lubricant 1-2 parts, light stabilizer 0.3-0.6 parts.

[0019] Preferably, the molecular weight of the high impact polystyrene resin is 73000-90000 g / mol;

[0020] The molecular weight of the polypropylene is 300000-350000 g / mol;

[0021] The compatibilizer A is polystyrene grafted with maleic anhydride;

[0022] The viscosity enhancer is modified amino-octapolyethylene glycol-carboxylic acid.

[0023] Preferably, the preparation method of the modified amino-octapolyethylene glycol-carboxylic acid is as follows:

[0024] Step A1. Soak the biochar in a KOH solution with a mass fraction of 35%-40%, stir for 12-13 hours, let stand for 20-24 hours, dry at 110-120°C for 48-50 hours, cool and wash twice with a 1 mol / L hydrochloric acid solution and deionized water, and then dry at 60-70°C for 3-4 hours to obtain modified biochar;

[0025] Step A2. Evenly mix the modified biochar, amino-octapolyethylene glycol-carboxylic acid and deionized water at 35-42° C., and then dry the mixture at 50-60° C. for 2-3 hours to obtain modified amino-octapolyethylene glycol-carboxylic acid.

[0026] Preferably, the mass ratio of the biochar to the 40% KOH solution in step A1 is 1:4.5-5.5;

[0027] The mass ratio of the modified biochar, amino-octapolyethylene glycol-carboxylic acid and deionized water in step A2 is 5-8:11-15:25-30.

[0028] Preferably, the preparation method of the toughening masterbatch is as follows:

[0029] Styrene-butadiene-styrene block copolymer and high-impact polystyrene are mixed, white oil is added while stirring, stirred at 100°C for 15 minutes, and then granulated by twin-screw extrusion after cooling to obtain toughened masterbatch;

[0030] The mass ratio of the styrene-butadiene-styrene block copolymer, high impact polystyrene and white oil is 5-8:10-13:3-5.

[0031] Preferably, the molecular weight of the polypropylene is 300000-350000 g / mol;

[0032] The molecular weight of the polystyrene is 230000-250000 g / mol;

[0033] The molecular weight of the polyethylene is 12000-26000 g / mol;

[0034] The compatibilizer B is obtained by mixing polypropylene grafted maleic anhydride, polystyrene grafted maleic anhydride, chlorinated polyethylene grafted maleic anhydride, and methyl methacrylate-butadiene-styrene in a mass ratio of 5-7:5-7:2-4:2-3.

[0035] Preferably, the toughening agent is obtained by mixing ethylene-vinyl acetate, styrene-butadiene-styrene block copolymer, and styrene-ethylene butene copolymer-styrene in a mass ratio of 2-4:5-8:5-8;

[0036] The light stabilizer is light stabilizer 770.

[0037] Preferably, the lubricant is any one of calcium stearate, solid paraffin, chlorinated paraffin, and ethylene bisstearamide.

[0038] Preferably, the antioxidant is obtained by mixing antioxidant 1010, antioxidant 168 and 2,2,6,6-tetramethylpiperidinyl oxide in a mass ratio of 10-12:3-4:4-5.

[0039] A method for preparing a composite plastic plate for a refrigerator liner comprises the following steps:

[0040] Step S1. High-impact polystyrene resin, polypropylene, toughening masterbatch, compatibilizer A and tackifier are sequentially added to a high-speed mixer and mixed for 10-15 minutes to obtain a mixture A;

[0041] Step S2. Add polypropylene, polystyrene, polyethylene, compatibilizer B, toughening agent, antioxidant, lubricant, and light stabilizer to a high-speed mixer and mix for 10-15 minutes to obtain a mixture B;

[0042] Step S3. Extruding the mixture A and the mixture B into a sheet by double-layer extrusion technology, the main machine extrusion process parameters are: zone 170-180°C, zone 2 temperature 200-210°C, zone 3 temperature 210-220°C, zone 4 temperature 220-230°C, zone 5 temperature 220-230°C, die head temperature 220-230°C, and main machine speed 300-450 rpm; the auxiliary machine extrusion process parameters are: zone 175-185°C, zone 2 temperature 205-215°C, zone 3 temperature 215-225°C, zone 4 temperature 225-235°C, zone 5 temperature 225-235°C, die head temperature 225-235°C, and main machine speed 300-450 rpm, to obtain a composite plastic plate for a refrigerator liner.

[0043] Beneficial effects of the present invention:

[0044] The present invention provides a composite plastic plate for refrigerator liner and a preparation method thereof. The present invention uses a double-layer extrusion technology to prepare a refrigerator liner with a modified high-impact polystyrene as the surface layer and a polypropylene-polystyrene alloy material as the bottom layer. Among them, the polypropylene in the polypropylene-polystyrene alloy material has low polarity and low solubility in oily substances, and is not easy to cause cracking of the refrigerator liner; the modified high-impact polystyrene has good adhesion to the polyurethane foam material, and the liner is not easy to separate from the shell at low temperatures.

[0045] The modified amino-octapolyethylene glycol-carboxylic acid in the modified high-impact polystyrene can stably exist at low temperatures, and the two ends of the molecule contain active groups that can react with the groups in the high-impact polystyrene and polyurethane to achieve cross-linking, which can effectively enhance the adhesion between the two, thereby effectively improving the problem of the refrigerator liner separating from the shell. Compared with the existing technology, it has a wide range of application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 This is a schematic diagram of a refrigerator liner prepared according to the present invention. DETAILED DESCRIPTION

[0048] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0049] The sources and properties of some of the raw materials used in the present invention are as follows:

[0050] High-impact polystyrene resin was purchased from Dongguan Xiangyi New Materials Co., Ltd.; polystyrene grafted maleic anhydride was purchased from Shanghai Jizhi Biochemical Technology Co., Ltd.; amino-octapolyethylene glycol-carboxylic acid was purchased from Shaanxi Xinyan Bomei Biotechnology Co., Ltd.; styrene-butadiene-styrene block copolymer was purchased from Germany's Jiaobao; polystyrene was purchased from Dushanzi Petrochemical Company; polypropylene was purchased from Shanghai Canxian Plastic Co., Ltd.; polyethylene was purchased from Dushanzi Petrochemical Company; light stabilizer 770 was purchased from Qingdao Jiedjia New Material Technology Co., Ltd.

[0051] Embodiment 1: A method for preparing a composite plastic plate for a refrigerator liner, comprising the following steps:

[0052] S1. Styrene-butadiene-styrene block copolymer and high-impact polystyrene are mixed, white oil is added while stirring, and the mixture is stirred at 100° C. for 15 minutes, wherein the mass ratio of styrene-butadiene-styrene block copolymer, high-impact polystyrene and white oil is 5:10:3, and after cooling, the mixture is extruded and granulated by a twin-screw extruder to obtain a toughened masterbatch;

[0053] S2. The biochar was immersed in a 35% KOH solution, and the mass ratio of the biochar to the 35% KOH solution was 1:5.5. The mixture was stirred for 12 hours, allowed to stand for 20 hours, and then dried at 110°C for 50 hours. After cooling, the mixture was washed twice with a 1 mol / L hydrochloric acid solution and deionized water, and then dried at 60°C for 4 hours to obtain modified biochar.

[0054] S3. The modified biochar, amino-octapolyethylene glycol-carboxylic acid and deionized water in a mass ratio of 5:11:25 were mixed uniformly at 35°C, and the mixture was dried at 50°C for 3 hours to obtain modified amino-octapolyethylene glycol-carboxylic acid;

[0055] S4. High-impact polystyrene resin, polypropylene, toughening masterbatch, compatibilizer and modified amino-octapolyethylene glycol-carboxylic acid in a mass ratio of 75:6:2:5:0.3 were sequentially added into a high-speed mixer and mixed for 10 minutes to obtain a mixture A;

[0056] S5. Polypropylene, polystyrene, polyethylene, compatibilizer B, toughening agent, antioxidant, lubricant, and light stabilizer in a mass ratio of 20:65:5:8:3:2:1:0.3 are sequentially added into a high-speed mixer and mixed for 10 minutes to obtain a mixture B;

[0057] S6. 4 g of mixture A and 96 g of mixture B are extruded into a sheet using a double-layer extrusion technology. The main extrusion process parameters are: 170°C in zone 1, 200°C in zone 2, 210°C in zone 3, 220°C in zone 4, 220°C in zone 5, die head temperature 220°C, and a main machine speed of 300 rpm; the auxiliary machine extrusion process parameters are: 175°C in zone 1, 205°C in zone 2, 215°C in zone 3, 225°C in zone 4, 225°C in zone 5, die head temperature 225°C, and a main machine speed of 300 rpm, to obtain a composite plastic plate for a refrigerator liner.

[0058] Embodiment 2: A method for preparing a composite plastic plate for a refrigerator liner, comprising the following steps:

[0059] S1. Styrene-butadiene-styrene block copolymer and high-impact polystyrene are mixed, white oil is added while stirring, and the mixture is stirred at 100° C. for 15 minutes, wherein the mass ratio of styrene-butadiene-styrene block copolymer, high-impact polystyrene and white oil is 6:11:4, and after cooling, the mixture is extruded and granulated by a twin-screw extruder to obtain a toughened masterbatch;

[0060] S2. The biochar was immersed in a 38% KOH solution, and the mass ratio of the biochar to the 38% KOH solution was 1:5. The mixture was stirred for 12.5 hours, allowed to stand for 22 hours, and then dried at 115°C for 49 hours. After cooling, the mixture was washed twice with a 1 mol / L hydrochloric acid solution and deionized water, and then dried at 65°C for 3.5 hours to obtain modified biochar.

[0061] S3. The modified biochar, amino-octapolyethylene glycol-carboxylic acid and deionized water in a mass ratio of 6:13:27 were mixed uniformly at 37°C, and the mixture was dried at 55°C for 2.5 hours to obtain modified amino-octapolyethylene glycol-carboxylic acid;

[0062] S4. High-impact polystyrene resin, polypropylene, toughening masterbatch, compatibilizer and modified amino-octapolyethylene glycol-carboxylic acid in a mass ratio of 78:7:2.5:6:0.5 were sequentially added into a high-speed mixer and mixed for 12 minutes to obtain a mixture A;

[0063] S5. Polypropylene, polystyrene, polyethylene, compatibilizer B, toughening agent, antioxidant, lubricant, and light stabilizer in a mass ratio of 22:67:7:10:5:2.5:1.5:0.4 were sequentially added into a high-speed mixer and mixed for 12 minutes to obtain a mixture B;

[0064] S6. 5g of mixture A and 95g of mixture B are extruded into a sheet using a double-layer extrusion technology. The main extrusion process parameters are: 175°C in zone 1, 205°C in zone 2, 215°C in zone 3, 225°C in zone 4, 225°C in zone 5, die head temperature 225°C, and a main machine speed of 350 rpm; the auxiliary machine extrusion process parameters are: 180°C in zone 1, 210°C in zone 2, 220°C in zone 3, 230°C in zone 4, 230°C in zone 5, die head temperature 230°C, and a main machine speed of 350 rpm, to obtain a composite plastic plate for a refrigerator liner.

[0065] Embodiment 3: A method for preparing a composite plastic plate for a refrigerator liner, comprising the following steps:

[0066] S1. Styrene-butadiene-styrene block copolymer and high-impact polystyrene are mixed, white oil is added while stirring, and the mixture is stirred at 100° C. for 15 minutes, wherein the mass ratio of styrene-butadiene-styrene block copolymer, high-impact polystyrene and white oil is 7:12:4, and after cooling, the mixture is extruded and granulated by a twin-screw extruder to obtain a toughened masterbatch;

[0067] S2. The biochar was immersed in a 38% KOH solution, and the mass ratio of the biochar to the 38% KOH solution was 1:5, stirred for 12.5 hours, allowed to stand for 20-24 hours, and then dried at 115°C for 49 hours. After cooling, it was washed twice with a 1 mol / L hydrochloric acid solution and deionized water, and then dried at 65°C for 3.5 hours to obtain modified biochar;

[0068] S3. The modified biochar, amino-octapolyethylene glycol-carboxylic acid and deionized water in a mass ratio of 7:13:27 were mixed uniformly at 37°C, and the mixture was dried at 55°C for 2.5 hours to obtain modified amino-octapolyethylene glycol-carboxylic acid;

[0069] S4. High-impact polystyrene resin, polypropylene, toughening masterbatch, compatibilizer and modified amino-octapolyethylene glycol-carboxylic acid in a mass ratio of 80:8:2.5:7:0.5 were sequentially added into a high-speed mixer and mixed for 14 minutes to obtain a mixture A;

[0070] S5: polypropylene, polystyrene, polyethylene, compatibilizer B, toughening agent, antioxidant, lubricant, and light stabilizer in a mass ratio of 25:70:7:10:5:2.5:1.5:0.5 are sequentially added into a high-speed mixer and mixed for 14 minutes to obtain a mixture B;

[0071] S6. 6 g of mixture A and 94 g of mixture B are extruded into a sheet using a double-layer extrusion technology. The main extrusion process parameters are: 175°C in zone 1, 205°C in zone 2, 215°C in zone 3, 225°C in zone 4, 225°C in zone 5, die head temperature 225°C, and a main machine speed of 350 rpm; the auxiliary machine extrusion process parameters are: 180°C in zone 1, 210°C in zone 2, 220°C in zone 3, 230°C in zone 4, 230°C in zone 5, die head temperature 230°C, and a main machine speed of 350 rpm, to obtain a composite plastic plate for a refrigerator liner.

[0072] Embodiment 4: A method for preparing a composite plastic plate for a refrigerator liner, comprising the following steps:

[0073] S1. Styrene-butadiene-styrene block copolymer and high-impact polystyrene are mixed, white oil is added while stirring, and the mixture is stirred at 100° C. for 15 minutes, wherein the mass ratio of styrene-butadiene-styrene block copolymer, high-impact polystyrene and white oil is 8:13:5, and after cooling, the mixture is extruded and granulated by a twin-screw extruder to obtain a toughened masterbatch;

[0074] S2. The biochar was soaked in a 40% KOH solution, and the mass ratio of the biochar to the 40% KOH solution was 1:4.5. The mixture was stirred for 13 hours, allowed to stand for 24 hours, and then dried at 120°C for 48 hours. After cooling, the mixture was washed twice with a 1 mol / L hydrochloric acid solution and deionized water, and then dried at 70°C for 3 hours to obtain modified biochar.

[0075] S3. The modified biochar, amino-octapolyethylene glycol-carboxylic acid and deionized water in a mass ratio of 8:15:30 were mixed uniformly at 42° C., and the mixture was dried at 60° C. for 2 h to obtain modified amino-octapolyethylene glycol-carboxylic acid;

[0076] S4. High-impact polystyrene resin, polypropylene, toughening masterbatch, compatibilizer and modified amino-octapolyethylene glycol-carboxylic acid in a mass ratio of 82:10:3:8:0.8 were sequentially added into a high-speed mixer and mixed for 15 minutes to obtain a mixture A;

[0077] S5. Polypropylene, polystyrene, polyethylene, compatibilizer B, toughening agent, antioxidant, lubricant, and light stabilizer in a mass ratio of 30:75:10:12:7:3:2:0.6 were sequentially added into a high-speed mixer and mixed for 15 minutes to obtain a mixture B;

[0078] S6. 8g of mixture A and 92g of mixture B are extruded into a sheet using a double-layer extrusion technology. The main extrusion process parameters are: 180°C in zone 1, 210°C in zone 2, 220°C in zone 3, 230°C in zone 4, 230°C in zone 5, die head temperature 230°C, and main machine speed 450 rpm; the auxiliary extrusion process parameters are: 185°C in zone 1, 215°C in zone 2, 225°C in zone 3, 235°C in zone 4, 235°C in zone 5, die head temperature 235°C, and main machine speed 450 rpm, to obtain a composite plastic plate for a refrigerator liner.

[0079] Comparative Example 1:

[0080] Compared with Example 1, this comparative example does not add modified amino-octapolyethylene glycol-carboxylic acid during the preparation of the composite plastic plate for the refrigerator liner, and the remaining steps and parameters are the same, which will not be repeated in this comparative example, and finally a composite plastic plate for the refrigerator liner is obtained.

[0081] Comparative Example 2:

[0082] Compared with Example 1, this comparative example only replaces "modified amino-octapolyethylene glycol-carboxylic acid" with "amino-octapolyethylene glycol-carboxylic acid", and the remaining steps and parameters are the same, which will not be repeated in this comparative example, and finally a composite plastic plate for a refrigerator liner is obtained.

[0083] Comparative Example 3:

[0084] Compared with Example 1, this comparative example only adjusts "4g of modified high-impact polystyrene, 96g of polypropylene-polystyrene alloy material" to "96g of modified high-impact polystyrene, 4g of polypropylene-polystyrene alloy material", and the remaining steps and parameters are the same, which will not be repeated in this comparative example, and finally a composite plastic plate for a refrigerator liner is obtained.

[0085] Performance Test:

[0086] Performance test of modified high impact polystyrene:

[0087] Density test:

[0088] Referring to the test standard GB / T1033.1-2008 "Determination of density of plastic non-foamed plastics Part 1: Immersion method, liquid pycnometer method and titration method", the density of the modified high-impact polystyrene prepared in Example 1 to Example 4 and Comparative Example 1 to Comparative Example 3 was measured, and the liquid used was distilled water;

[0089] Density calculation formula:

[0090] Density = (m2-m1)÷(m3-m2)×ρ 液

[0091] Wherein, m1 is the mass of the empty pycnometer, m2 is the total mass of the pycnometer and modified high-impact polystyrene, and m3 is the total mass of the pycnometer, modified high-impact polystyrene and distilled water;

[0092] Mechanical properties test:

[0093] Referring to the ISO527 test standard, the modified high-impact polystyrene prepared in Example 1 to Example 4 and Comparative Example 1 to Comparative Example 3 was tested for tensile strength using a universal electronic tensile testing machine at a tensile rate of 50 mm / min, a test temperature of (23±2)°C, and a humidity of 50%±3%;

[0094] Referring to the ISO7619 test standard, the modified high-impact polystyrene prepared in Example 1 to Example 4 and Comparative Example 1 to Comparative Example 3 was tested for cantilever notched impact strength using a cantilever beam impact tester at a test temperature of (23±2)°C and a humidity of 50%±3%.

[0095] The modified high-impact polystyrene prepared in Examples 1 to 4 and Comparative Examples 1 to 3 was placed in an ESCR fixture for bending and oiling to obtain bent non-oiled specimens and bent oiled specimens. At the same time, non-bending oiled specimens in a flat state were prepared, and the tensile properties of the specimens in different states were tested, and the tensile properties of the blank specimens (non-bending, non-oiled) were compared to calculate the change rate of tensile strength;

[0096] The modified high-impact polystyrene and polyurethane foam materials prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were respectively used to prepare refrigerator liners, and the refrigerator liners were placed at (-30±5)°C for 6 months to observe whether the refrigerator liners were detached from the shell.

[0097] Performance test of polypropylene-polystyrene alloy material:

[0098] Density test:

[0099] Referring to the test standard GB / T1033.1-2008 "Determination of density of non-foamed plastics Part 1: Immersion method, liquid pycnometer method and titration method", the density of the polypropylene-polystyrene alloy material prepared in Example 1 to Example 4 and Comparative Example 1 to Comparative Example 3 was measured, and the liquid used was distilled water;

[0100] Density calculation formula:

[0101] Density = (m2-m1)÷(m3-m2)×ρ 液

[0102] Among them, m1 is the mass of the empty pycnometer, m2 is the total mass of the pycnometer and the polypropylene-polystyrene alloy material, and m3 is the total mass of the pycnometer, the polypropylene-polystyrene alloy material, and the distilled water;

[0103] Mechanical properties test:

[0104] Referring to the ISO527 test standard, the tensile strength test of the polypropylene-polystyrene alloy materials prepared in Examples 1 to 4 and Comparative Examples 1 to 3 was performed using a universal electronic tensile testing machine at a tensile rate of 50 mm / min, a test temperature of (23±2)°C, and a humidity of 50%±3%;

[0105] Referring to the ISO7619 test standard, the polypropylene-polystyrene alloy materials prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to a cantilever beam notched impact strength test using a cantilever beam impact tester, with a test temperature of (23±2)°C and a humidity of 50%±3%.

[0106] The polypropylene-polystyrene alloy materials prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were placed in an ESCR fixture for bending and oiling to obtain bent non-oiled specimens and bent oiled specimens. At the same time, non-bending oiled specimens in a flat state were prepared, and the tensile properties of the specimens in different states were tested, and the tensile properties of the blank specimens (non-bending, non-oiled) were compared to calculate the change rate of tensile strength;

[0107] Table 1 Summary of experimental data of modified high impact polystyrene prepared in Example 1-Example 4 and Comparative Example 1-Comparative Example 3

[0108]

[0109] Table 2 Summary of experimental data of polypropylene-polystyrene alloy materials prepared in Example 1-Example 4 and Comparative Example 1-Comparative Example 3

[0110]

[0111]

[0112] Data Analysis:

[0113] It can be seen from Table 1 and Table 2 that the composite plastic plate for refrigerator liner prepared by the present invention has better mechanical properties and adhesion, which may be due to the good chemical stability of polypropylene in the polypropylene-polystyrene alloy material, low polarity, low solubility in oily substances, and is not easy to cause cracking of the refrigerator liner; the modified high-impact polystyrene modified amino-octapolyethylene glycol-carboxylic acid can stably exist at low temperatures, and the two ends of the molecule contain active groups, which can react with the groups in high-impact polystyrene and polyurethane to achieve cross-linking, and can effectively enhance the adhesion between the two; the modified biochar itself has good thermal stability, and adding it to composite materials such as resin can effectively enhance its tensile strength, and can also be used as a carrier of amino-octapolyethylene glycol-carboxylic acid to provide a layer of protection, thereby effectively improving the problem of the refrigerator liner leaving the shell;

[0114] In Comparative Example 1, since modified amino-octapolyethylene glycol-carboxylic acid was not added during the preparation of the composite plastic plate for the refrigerator liner, it can be seen from Tables 1 and 2 that its mechanical properties and adhesion are poor. This may be because the modified amino-octapolyethylene glycol-carboxylic acid interacts with the polar groups in the high-impact polystyrene to increase the intermolecular force inside the material, thereby improving the mechanical strength and toughness of the material and showing higher mechanical properties; at the same time, the molecule contains amino and carboxyl groups at both ends, which can cross-link with high-impact polystyrene and polyurethane materials to improve the adhesion between the two, and thus the liner is not easily separated from the shell. Therefore, the mechanical properties and adhesion shown in Comparative Example 1 are worse than those in Example 1; Comparative Example 2 replaces "modified amino-octapolyethylene glycol-carboxylic acid" with "amino-octapolyethylene glycol-carboxylic acid". It can be seen from Tables 1 and 2 that its mechanical properties and adhesion are poor. This may be due to the modified biological Carbon is used as a carrier, and its high specific surface area protects the active groups in amino-octapolyethylene glycol-carboxylic acid, avoiding the formation of chemical bonds with other additives in the modified high-impact polystyrene, and the modified biochar itself has good thermal stability, and can be used as a filler for the resin material to enhance its mechanical properties such as tensile strength. Therefore, the mechanical properties and adhesion exhibited by Comparative Example 2 are worse than those in Example 1; Comparative Example 3 adjusts "modified high-impact polystyrene 4g, polypropylene-polystyrene alloy material 96g" to "modified high-impact polystyrene 96g, polypropylene-polystyrene alloy material 4g", and it can be seen from Tables 1 and 2 that its mechanical properties and adhesion are poor. This may be due to the excessive content of modified high-impact polystyrene, which leads to a decrease in the overall rigidity of the composite material, and the high content of modified high-impact polystyrene has poor compatibility with the polypropylene-polystyrene alloy material. Therefore, the mechanical properties and adhesion exhibited by Comparative Example 3 are worse than those in Example 1.

[0115] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0116] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A composite plastic plate for refrigerator liner, characterized in that: The composite plastic board comprises a surface layer and a bottom layer; The surface layer is an auxiliary material, and the bottom layer is a main material; The auxiliary material is modified high-impact polystyrene; The main material is polypropylene-polystyrene alloy material; The mass ratio of the modified high-impact polystyrene to the polypropylene-polystyrene alloy material is 4-8:92-96; The modified high-impact polystyrene is prepared from the following raw materials in parts by weight: High impact polystyrene resin 75-82 parts, polypropylene 6-10 parts, toughening masterbatch 2-3 parts, compatibilizer A 5-8 parts, tackifier 0.3-0.8 parts; The polypropylene-polystyrene alloy material is prepared from the following raw materials in parts by weight: Polypropylene 20-30 parts, polystyrene 65-75 parts, polyethylene 5-10 parts, compatibilizer B 8-12 parts, toughening agent 3-7 parts, antioxidant 2-3 parts, lubricant 1-2 parts, light stabilizer 0.3-0.6 parts.

2. The composite plastic plate for refrigerator liner according to claim 1, characterized in that: The molecular weight of the high impact polystyrene resin is 73000-90000 g / mol; The molecular weight of the polypropylene is 300000-350000 g / mol; The compatibilizer A is polystyrene grafted with maleic anhydride; The viscosity enhancer is modified amino-octapolyethylene glycol-carboxylic acid.

3. The composite plastic plate for refrigerator liner according to claim 2, characterized in that: The preparation method of the modified amino-octapolyethylene glycol-carboxylic acid is as follows: Step A1. Soak the biochar in a KOH solution with a mass fraction of 35%-40%, stir for 12-13 hours, let stand for 20-24 hours, dry at 110-120°C for 48-50 hours, cool and wash twice with a 1 mol / L hydrochloric acid solution and deionized water, and then dry at 60-70°C for 3-4 hours to obtain modified biochar; Step A2. Evenly mix the modified biochar, amino-octapolyethylene glycol-carboxylic acid and deionized water at 35-42° C., and then dry the mixture at 50-60° C. for 2-3 hours to obtain modified amino-octapolyethylene glycol-carboxylic acid.

4. The composite plastic plate for refrigerator liner according to claim 3, characterized in that: The mass ratio of the biochar to the 40% KOH solution in step A1 is 1:4.5-5.5; The mass ratio of the modified biochar, amino-octapolyethylene glycol-carboxylic acid and deionized water in step A2 is 5-8:11-15:25-30.

5. The composite plastic plate for refrigerator liner according to claim 1, characterized in that: The preparation method of the toughening masterbatch is as follows: Styrene-butadiene-styrene block copolymer and high-impact polystyrene are mixed, white oil is added while stirring, stirred at 100°C for 15 minutes, and then granulated by twin-screw extrusion after cooling to obtain toughened masterbatch; The mass ratio of the styrene-butadiene-styrene block copolymer, high impact polystyrene and white oil is 5-8:10-13:3-5.

6. The composite plastic plate for refrigerator liner according to claim 1, characterized in that: The molecular weight of the polypropylene is 300000-350000 g / mol; The molecular weight of the polystyrene is 230000-250000 g / mol; The molecular weight of the polyethylene is 12000-26000 g / mol; The compatibilizer B is obtained by mixing polypropylene grafted maleic anhydride, polystyrene grafted maleic anhydride, chlorinated polyethylene grafted maleic anhydride, and methyl methacrylate-butadiene-styrene in a mass ratio of 5-7:5-7:2-4:2-3.

7. The composite plastic plate for refrigerator liner according to claim 1, characterized in that: The toughening agent is obtained by mixing ethylene-vinyl acetate, styrene-butadiene-styrene block copolymer, and styrene-ethylene butene copolymer-styrene in a mass ratio of 2-4:5-8:5-8; The light stabilizer is light stabilizer 770.

8. The composite plastic plate for refrigerator liner according to claim 1, characterized in that: The lubricant is any one of calcium stearate, solid paraffin, chlorinated paraffin, and ethylene bis stearamide.

9. The composite plastic plate for refrigerator liner according to claim 1, characterized in that: The antioxidant is obtained by mixing antioxidant 1010, antioxidant 168 and 2,2,6,6-tetramethylpiperidinyl oxide in a mass ratio of 10-12:3-4:4-5.

10. A method for preparing the composite plastic board for refrigerator liner according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step S1. High-impact polystyrene resin, polypropylene, toughening masterbatch, compatibilizer A and tackifier are sequentially added to a high-speed mixer and mixed for 10-15 minutes to obtain a mixture A; Step S2. Add polypropylene, polystyrene, polyethylene, compatibilizer B, toughening agent, antioxidant, lubricant, and light stabilizer to a high-speed mixer and mix for 10-15 minutes to obtain a mixture B; Step S3. Extruding the mixture A and the mixture B into a sheet by double-layer extrusion technology, the main machine extrusion process parameters are: zone 170-180°C, zone 2 temperature 200-210°C, zone 3 temperature 210-220°C, zone 4 temperature 220-230°C, zone 5 temperature 220-230°C, die head temperature 220-230°C, and main machine speed 300-450 rpm; the auxiliary machine extrusion process parameters are: zone 175-185°C, zone 2 temperature 205-215°C, zone 3 temperature 215-225°C, zone 4 temperature 225-235°C, zone 5 temperature 225-235°C, die head temperature 225-235°C, and main machine speed 300-450 rpm, to obtain a composite plastic plate for a refrigerator liner.

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