Thermoplastic EPS (Expandable Polystyrene) foam packaging material

Abstract

Belonging to the technical field of high polymer materials, the invention discloses a thermoplastic EPS foam packaging material, which comprises 20-35 parts of EPS, 20-25 parts of modified organosilicon coating, 0-4 parts of acrylic resin and 2-5 parts of expandable graphite. The modified organic silicon coating is used as a binder for coating EPS, so that the thermal stability and char forming property of the EPS packaging material are effectively improved, the LOI value of a foam sample can be obviously improved, and the packaging material can reach the UL-94 V-0 flame retardant grade; therefore, the thermoplastic EPS foam packaging material provided by the invention solves the technical problem of how to improve the flame retardant property of the EPS foam packaging material.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, in particular to a thermoplastic EPS foam packaging material. Background Art

[0002] Among polymer materials, polystyrene foam is a commonly used packaging material; the polystyrene foam is mainly a foam material obtained by mixing polystyrene resin, physical foaming agent and other processing aids. According to different molding methods, polystyrene foam can be divided into expandable polystyrene foam, namely EPS, and extruded polystyrene foam, namely XPS. EPS is first obtained by injecting soluble pentane and other additives into polystyrene hollow resin to obtain unfoamed beads; then, the foam material is prepared by subsequent mold foaming molding. XP$ is mainly a hard foam material obtained by mixing polystyrene resin and its copolymers with additives such as foaming agents and catalysts, and then extruding them under heating and pressure. Both types of polystyrene foam have their own advantages, but from the perspectives of durability, dimensional stability and economy, EPS is still the first choice in the domestic and foreign markets, and the current use of EPS shows an increasing trend year by year.

[0003] The reason why EPS can occupy an important position among many foam materials is because of its many excellent properties. First, in the complete closed-cell honeycomb structure inside EPS, the volume of the mixture of air and foaming agent can be as high as more than 98%. Since the thermal conductivity of these mixtures is very low, EPS has good thermal insulation performance; therefore, EPS is often used as building insulation and packaging materials. Secondly, compared with other packaging and civil engineering materials, the density of EPS is very small, usually between 15~40kg / m 3 This can greatly reduce the manpower and material costs in its application process. In addition, EPS's good acid and alkali resistance, antistatic properties, hydrophobicity and mechanical properties also make it widely used in many fields, such as roads, ships and automobiles.

[0004] Based on this, Chinese patent CN106079219B discloses a production process for EPS foam packaging boxes, which includes: pre-expansion, maturation and molding processes; the maturation process includes: transporting EPS foam particles to a pressure tank; filling the tank with hot air at a pressure of 0.4 to 0.6 kgf / cm2 and a temperature of 35 to 45 degrees Celsius; maintaining the hot air pressure and temperature in the tank constant, and storing EPS foam particles for 0.5 to 1 hour; filling the tank with hot air again to increase the pressure inside the tank to 0.8 to 1.2 kgf / cm2; maintaining the pressure and temperature inside the tank constant, and storing EPS foam particles for 0.8 to 1.2 hours; filling the tank with hot air again to increase the pressure inside the tank to 1.8 to 2.2 kgf / cm2; maintaining the pressure and temperature inside the tank constant, and storing EPS foam particles for 0.8 to 1.2 hours to complete maturation. In this production process, the maturation treatment is carried out by using a pressurization and temperature increase method, and the maturation effect is good, and the negative pressure recovery rate in the bubble cell reaches 99%.

[0005] However, the EPS foam produced by the EPS foam packaging box production process disclosed above still has the technical problem of insufficient flame retardancy. Specifically, due to the molecular structure of the EPS main chain rich in hydrocarbons, the side chain rich in a large number of aromatic rings, and the high air circulation inside the pores, it is highly flammable and can be ignited instantly after contacting a fire source, and a large amount of black smoke, toxic gases and molten droplets will be generated during the combustion process. When a fire occurs, it is not conducive to escape and rescue work; therefore, how to perform flame retardant modification on EPS foam is a technical problem that needs to be solved urgently in the current promotion of EPS packaging materials. Summary of the invention

[0006] Based on this, it is necessary to provide a thermoplastic EPS foam packaging material to address the technical issue of how to improve the flame retardant properties of EPS foam packaging materials.

[0007] A thermoplastic EPS foam packaging material comprises, by weight, 20-35 parts of EPS, 20-25 parts of modified organic silicon coating, 0-4 parts of acrylic resin and 2-5 parts of expandable graphite.

[0008] Specifically, an embodiment includes, by mass, 20 parts of EPS, 20 parts of modified silicone coating, 2 parts of acrylic resin and 2 parts of expandable graphite.

[0009] Specifically, another embodiment includes, by mass, 35 parts of EPS, 25 parts of modified silicone coating, 4 parts of acrylic resin and 5 parts of expandable graphite.

[0010] Specifically, another embodiment includes, by mass, 25 parts of EPS, 23 parts of modified silicone coating, 2 parts of acrylic resin and 3 parts of expandable graphite.

[0011] Specifically, another embodiment includes, by mass, 25 parts of EPS, 22 parts of modified silicone coating and 3 parts of expandable graphite.

[0012] Specifically, another embodiment includes, by mass, 25 parts of EPS, 20 parts of modified silicone coating, 4 parts of acrylic resin, and 5 parts of expandable graphite.

[0013] Specifically, in another embodiment, the modified silicone coating includes, by mass, 60-75 parts of silicone resin, 15-25 parts of epoxy resin, 10-15 parts of polyamide resin, 15-25 parts of toluene and 0.5-1 part of catalyst.

[0014] Specifically, in another embodiment, the modified silicone coating includes, by mass, 60 parts of silicone resin, 15 parts of epoxy resin, 15 parts of polyamide resin, 15 parts of toluene and 0.5 parts of catalyst.

[0015] Specifically, in another embodiment, the modified silicone coating includes, by mass, 75 parts of silicone resin, 25 parts of epoxy resin, 10 parts of polyamide resin, 25 parts of toluene and 1 part of catalyst.

[0016] Specifically, in another embodiment, the modified silicone coating includes, by mass, 65 parts of silicone resin, 20 parts of epoxy resin, 12 parts of polyamide resin, 20 parts of toluene and 0.5 parts of catalyst.

[0017] In summary, the present invention discloses a thermoplastic EPS foam packaging material, which comprises, by weight, 20-35 parts of EPS, 20-25 parts of modified silicone coating, 0-4 parts of acrylic resin and 2-5 parts of expandable graphite. The present invention effectively improves the thermal stability and carbonization of the EPS packaging material by using the modified silicone coating as a binder for coating EPS, which can significantly improve the LOI value of the foam sample, and can also enable the packaging material to reach the flame retardant grade of UL-94 V-0; this is because the use of the modified silicone coating as a binder can effectively reduce the amount of expandable graphite added; it can also reduce its fly ash behavior, and the addition of expandable graphite also increases the graphitization degree of the residual carbon. The synergistic flame retardant effect between the modified silicone coating and the expandable graphite enables the thermoplastic EPS foam material to form a Si-OC cross-linked carbon layer during the combustion process to isolate the flame and the combustible gas, thereby reducing heat transfer to play a flame retardant role. Therefore, the thermoplastic EPS foam packaging material of the present invention solves the technical problem of how to improve the flame retardant performance of the EPS foam packaging material. DETAILED DESCRIPTION

[0018] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with specific embodiments. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0019] Specifically, the thermoplastic EPS foam packaging material of the present invention comprises the following components, measured by mass: 20-35 parts of EPS, 20-25 parts of modified organic silicon coating, 0-4 parts of acrylic resin and 2-5 parts of expandable graphite.

[0020] Specifically, in the technical solution of a thermoplastic EPS foam packaging material of the present invention, several specific embodiments are as follows: Example 1

[0021] 20 parts of EPS, 20 parts of modified silicone coating, 2 parts of acrylic resin and 2 parts of expandable graphite. Example 2

[0022] EPS 35 parts, modified silicone coating 25 parts, acrylic resin 4 parts and expandable graphite 5 parts. Example 3

[0023] EPS 25 parts, modified silicone coating 23 parts, acrylic resin 2 parts and expandable graphite 3 parts. Example 4

[0024] EPS 25 parts, modified silicone coating 22 parts and expandable graphite 3 parts. Example 5

[0025] EPS 25 parts, modified silicone coating 20 parts, acrylic resin 4 parts, expandable graphite 5 parts.

[0026] Further, a method for preparing the aforementioned thermoplastic EPS foam packaging material comprises the following steps: S1: Prepare each material according to the preset ratio; S2: pre-foaming the original EPS beads in an expansion device at 100°C for 3 minutes to obtain pre-foamed EPS beads; and aging the pre-foamed EPS beads at 25±3°C for 24 hours; S3: evenly dispersing expandable graphite in the modified silicone coating; then, coating the mixture of expandable graphite and modified silicone coating on the surface of pre-foamed EPS beads until the surface of the pre-foamed EPS beads is evenly coated; S4: The coated EPS beads are transferred to a 70°C oven for drying until they no longer lose weight, and then placed in a molding mold for secondary foaming at a temperature of 120±3°C and a time of 145 min; S5: Finally, the formed EPS foam material is taken out from the mold and then subjected to subsequent machining processes such as trimming.

[0027] Furthermore, in a technical solution of a thermoplastic EPS foam packaging material of the present invention, the modified silicone coating includes, by mass, 60-75 parts of silicone resin, 15-25 parts of epoxy resin, 10-15 parts of polyamide resin, 15-25 parts of toluene and 0.5-1 part of catalyst.

[0028] Specifically, in the formula of modified silicone coating, silicone resin can be used as the main component of the coating because of its excellent heat resistance, weather resistance and chemical resistance. The epoxy resin can be bisphenol A epoxy resin, because it has strong adhesion, and its hydroxyl and ether groups have strong polarity, which can produce strong effects with adjacent interfaces, thereby improving the adhesion and mechanical strength of the coating. More specifically, through the grafting condensation reaction between the epoxy group and hydroxyl group of the epoxy resin and the active group of the polysiloxane, the modified epoxy / silicone coating has good stability and has the advantages of both epoxy resin and silicone resin; this modification technology can improve the stability, temperature resistance, corrosion resistance, etc. of the coating.

[0029] Furthermore, the low molecular weight polyamide resin can be used as a curing agent for the modified silicone coating to cure the coating into a film after construction. The toluene can be used as a solvent for the system to dissolve the epoxy resin and adjust the viscosity of the coating. The catalyst is used to promote the condensation reaction between the epoxy resin and the silicone resin, and an organic metal compound can usually be used as the catalyst, for example, ferrocene, diethyl zinc, methyl potassium or ethyl magnesium.

[0030] Specifically, in the aforementioned modified silicone coating ratio, several specific embodiments are as follows: Formula 1 of modified silicone coating: 60 parts of silicone resin, 15 parts of epoxy resin, 15 parts of polyamide resin, 15 parts of toluene and 0.5 parts of catalyst.

[0031] Formula 2 of modified silicone coating: 75 parts of silicone resin, 25 parts of epoxy resin, 10 parts of polyamide resin, 25 parts of toluene and 1 part of catalyst.

[0032] Formula three of modified silicone coating: 65 parts of silicone resin, 20 parts of epoxy resin, 12 parts of polyamide resin, 20 parts of toluene and 0.5 parts of catalyst.

[0033] Specifically, the above-mentioned modified silicone coating, its specific preparation process includes the following steps: S11: dissolving the epoxy resin in toluene, and heating the system temperature to 120±5°C to cause reflux; S12: adding a catalyst to the dissolved epoxy resin to promote a subsequent condensation reaction; S13: adding silicone resin according to a preset ratio, and performing a constant temperature reaction at a temperature of 120±1° C. to cause a condensation reaction between the epoxy resin and the silicone resin to form an epoxy-modified silicone resin; S14: During the reaction, it is necessary to reduce the pressure to remove the water generated by the condensation reaction to ensure the smooth progress of the reaction; S15: mixing the synthesized epoxy-modified silicone resin and the polyamide resin in a preset ratio to form a two-component coating system; S16: Finally, appropriate amounts of additives such as dispersants, thickeners, etc. can be added as needed to improve the dispersibility and stability of the coating; the viscosity of the coating can also be adjusted by adding solvents or thickeners.

[0034] Furthermore, the flame retardant properties of the thermoplastic EPS foam packaging material of the present invention can be tested by limiting oxygen index, i.e., LOI, and vertical burning test, i.e., UL-94 related test standards. The specific experimental data are shown in Table 1.

[0035] Specifically, in the LOI test, according to the relevant test standards of ASTM D2863, the EPS foam can be prepared into a long strip sample of 130mm×10mm×10mm, and the flame is ignited from the top of the sample. The pre-ignition length of the sample is 0.5m. If the sample can be ignited, the timing starts after reaching the pre-ignition length. During this period, the ratio of N2 and O2 is adjusted so that the burning length of the sample at 3 minutes just reaches 5cm. At this time, the corresponding oxygen content is the minimum oxygen content that can ignite the material, that is, the LOI value of the material. If the sample fails to ignite, the ratio of N2 and O2 needs to be readjusted to meet the test standard.

[0036] In the UL-94 test, according to the relevant test standard of ASTM D3801, EPS foam is prepared into a long strip sample of 130mm×19mm×19mm. The foam sample is hung vertically to ensure that it does not shake. Absorbent cotton is placed 10©m below the sample and ignited with an igniter with a flame length of about 2cm. For the first ignition, the igniter is placed at the bottom of the sample and ignited for 10s before being removed. The first self-extinguishing time of the sample combustion phenomenon is recorded, i.e. t1. After the extinguishing, the second ignition is continued. Similarly, the flame is removed 10s after ignition to observe the combustion phenomenon and record the second self-extinguishing time, i.e. t2.

[0037] Table 1: Flame retardant properties of thermoplastic EPS foam materials

[0038] It can be seen that the five embodiments disclosed by the thermoplastic EPS foam packaging material of the present invention can all achieve good flame retardant effect.

[0039] In summary, the present invention discloses a thermoplastic EPS foam packaging material, which comprises, by weight, 20-35 parts of EPS, 20-25 parts of modified silicone coating, 0-4 parts of acrylic resin and 2-5 parts of expandable graphite. The present invention effectively improves the thermal stability and carbonization of the EPS packaging material by using the modified silicone coating as a binder for coating EPS, which can significantly improve the LOI value of the foam sample, and can also enable the packaging material to reach the flame retardant grade of UL-94 V-0; this is because the use of the modified silicone coating as a binder can effectively reduce the amount of expandable graphite added; it can also reduce its fly ash behavior, and the addition of expandable graphite also increases the graphitization degree of the residual carbon. The synergistic flame retardant effect between the modified silicone coating and the expandable graphite enables the thermoplastic EPS foam material to form a Si-OC cross-linked carbon layer during the combustion process to isolate the flame and the combustible gas, thereby reducing heat transfer to play a flame retardant role. Therefore, the thermoplastic EPS foam packaging material of the present invention solves the technical problem of how to improve the flame retardant performance of the EPS foam packaging material.

[0040] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0041] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A thermoplastic EPS foam packaging material, characterized in that: Calculated by weight, it includes: 20-35 parts of EPS, 20-25 parts of modified silicone coating, 0-4 parts of acrylic resin and 2-5 parts of expandable graphite.

2. A thermoplastic EPS foam packaging material according to claim 1, characterized in that: Calculated by mass, it includes: 20 parts of EPS, 20 parts of modified silicone coating, 2 parts of acrylic resin and 2 parts of expandable graphite.

3. The thermoplastic EPS foam packaging material according to claim 1, characterized in that: Calculated by mass, it includes: 35 parts of EPS, 25 parts of modified silicone coating, 4 parts of acrylic resin and 5 parts of expandable graphite.

4. The thermoplastic EPS foam packaging material according to claim 1, characterized in that: Calculated by mass, it includes: 25 parts of EPS, 23 parts of modified silicone coating, 2 parts of acrylic resin and 3 parts of expandable graphite.

5. The thermoplastic EPS foam packaging material according to claim 1, characterized in that: Calculated by mass, it includes: 25 parts of EPS, 22 parts of modified silicone coating and 3 parts of expandable graphite.

6. The thermoplastic EPS foam packaging material according to claim 1, characterized in that: Calculated by mass, it includes: 25 parts of EPS, 20 parts of modified silicone coating, 4 parts of acrylic resin, and 5 parts of expandable graphite.

7. The thermoplastic EPS foam packaging material according to claim 1, characterized in that: The modified organic silicon coating comprises, by weight, 60-75 parts of organic silicon resin, 15-25 parts of epoxy resin, 10-15 parts of polyamide resin, 15-25 parts of toluene and 0.5-1 part of catalyst.

8. A thermoplastic EPS foam packaging material according to claim 7, characterized in that: The modified organic silicon coating comprises, by mass, 60 parts of organic silicon resin, 15 parts of epoxy resin, 15 parts of polyamide resin, 15 parts of toluene and 0.5 parts of catalyst.

9. The thermoplastic EPS foam packaging material according to claim 7, characterized in that: The modified organic silicon coating comprises, by mass, 75 parts of organic silicon resin, 25 parts of epoxy resin, 10 parts of polyamide resin, 25 parts of toluene and 1 part of catalyst.

10. The thermoplastic EPS foam packaging material according to claim 7, characterized in that: The modified organic silicon coating comprises, by weight, 65 parts of organic silicon resin, 20 parts of epoxy resin, 12 parts of polyamide resin, 20 parts of toluene and 0.5 parts of catalyst.

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