A BMC material for preparing a food contact article and a method for preparing the same

Abstract

This invention discloses a BMC material for preparing food contact products and its preparation method. The material comprises the following components by mass percentage: 12%–20% food contact grade styrene-based unsaturated polyester resin (compliant with GB 4806.7-2016); 3%–10% solvent-free PMMA powder; 0.5%–1% zinc stearate; 0.2%–0.6% curing agent TBIC; 0.01%–0.1% polymerization inhibitor TBHQ; 0.01%–0.05% stabilizer BHT; 20%–45% calcium carbonate; 10%–40% aluminum hydroxide; and 5%–10% glass fiber. This invention, by using low-cost food contact grade styrene-based resin combined with solvent-free PMMA powder and optimizing the ratio of TBIC to TBHQ, achieves near-zero styrene monomer residue in the product while reducing costs. This effectively solves the problems of high cost, difficulty in processability adjustment, and monomer residue risk associated with traditional food contact grade BMC materials. The cost of the resulting material can be controlled below 7 yuan / kg, and it has both flame-retardant and high-strength properties, making it a widely viable alternative to traditional food contact grade plastics.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, and in particular to a low-cost BMC material for preparing food contact articles. Background Technology

[0002] Bulk Molding Compound (BMC) is a fiber-reinforced thermosetting composite material made by mixing thermosetting resin as a matrix with chopped glass fibers, inorganic fillers, and various additives. Due to its high designability, high flowability, excellent flame retardancy, high strength, and low cost, BMC is widely used in industrial products, but its application in food contact products is very limited.

[0003] Currently, commercially available food contact grade BMC materials mainly use styrene-free resin systems, such as unsaturated polyester resins with methyl methacrylate (MMA) as the active monomer, combined with food contact grade additives to meet food safety requirements. However, this technical approach has the following prominent problems: First, styrene-free resins and their supporting additives are expensive, resulting in material costs as high as 25-35 yuan / kg, which greatly limits their widespread application; second, the processing performance of this type of resin is difficult to adjust, and the cost fluctuates greatly (10%-15%) when adjusting the formula, making it difficult to meet the molding requirements of complex products; in addition, due to the use of non-styrene active monomers, a certain amount of monomer residue still exists in the products, which, although non-toxic, poses an exposure risk and affects consumer acceptance.

[0004] On the other hand, although ordinary industrial-grade BMC materials use inexpensive styrene-based unsaturated polyester resin (costing about 10-15 yuan / kg), the large amount of styrene residue after curing results in excessive release of styrene and other harmful substances after product molding, failing to meet the migration and sensory testing requirements of food contact materials standards such as GB 4806.7. Therefore, they cannot be used in food contact products.

[0005] For example, Chinese patent CN119752138A discloses a styrene-free modified BMC molding compound, which has achieved food contact grade applications, but still has problems such as high cost and difficulty in processability adjustment, making it difficult to effectively replace traditional food contact grade plastics.

[0006] In conclusion, developing a BMC material that combines low cost, excellent processing performance, low monomer residue, and compliance with food contact safety requirements has significant market value and practical implications. Summary of the Invention

[0007] The purpose of this invention is to provide a low-cost BMC material for preparing food contact articles.

[0008] To address the above technical problems, this invention provides a BMC material for preparing food contact articles, comprising the following components by mass percentage: 12%~20% food contact grade styrene-type unsaturated polyester resin, wherein the styrene-type unsaturated polyester resin meets the requirements of GB 4806.7-2016 standard; 3%~10% solvent-free polymethyl methacrylate (PMMA) powder; 0.5%~1% zinc stearate; 0.2%~0.6% of curing agent tert-butyl isopropyl peroxide (TBIC); 0.01%~0.1% of polymerization inhibitor tert-butylhydroquinone (TBHQ); 0.01%~0.05% of the stabilizer butylated hydroxytoluene (BHT); 20%~45% calcium carbonate; 10%~40% aluminum hydroxide; 5%~10% glass fiber; The sum of the above components is 100%.

[0009] Preferably, the product comprises the following components by mass percentage: 15.18% food contact grade styrene-based unsaturated polyester resin, 4.28% solvent-free polymethyl methacrylate (PMMA) powder; 0.93% zinc stearate; 0.39% curing agent TBIC; 0.08% of polymerization inhibitor TBHQ; 0.02% stabilizer BHT; 42.8% calcium carbonate; 29.18% aluminum hydroxide; 7.14% glass fiber.

[0010] Furthermore, the amount of styrene monomer migration in the cured product of the BMC material is less than 0.01 mg / kg.

[0011] Preferably, the ratio of curing agent TBIC to polymerization inhibitor TBHQ is between 4:1 and 6:1.

[0012] The present invention also provides a method for preparing the above-mentioned BMC material for preparing food contact articles, comprising the following steps: S1 involves adding unsaturated polyester resin, low-shrinkage additives, mold release agents, curing agents, polymerization inhibitors, stabilizers, etc., into a high-speed disperser and mixing them to obtain a resin liquid. S2 adds calcium carbonate powder and aluminum hydroxide powder to a kneader and kneads them to obtain a mixed powder. S3 mixes the resin liquid with the mixed powder in a kneader to obtain a resin paste; S4 then adds glass fiber to the kneader containing the resin paste, kneads it, and obtains BMC material.

[0013] Preferably, after step S4, step S5 further includes removing the BMC material from the kneader, bagging and packaging it to obtain the finished product.

[0014] Preferably, the mixing time in S1 is 15-25 minutes.

[0015] Preferably, the kneading time in S2 is 15-25 minutes.

[0016] Preferably, the kneading time in S3 is 15-25 minutes.

[0017] Preferably, the kneading time in S4 is 8-12 minutes.

[0018] This invention achieves styrene monomer-free products by using low-cost food-contact grade styrene-type unsaturated polyester resin, combined with a special curing system and low-shrinkage agent system, resulting in cost reduction of more than 2.5 yuan / kg. Furthermore, the processability is easily adjustable, and the cost fluctuates little, effectively expanding the application range of food-contact grade BMC materials. These materials can be used to replace traditional food-contact grade plastics and also have characteristics such as flame retardancy and high strength. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to specific examples.

[0020] The components, raw materials, and formulations in the various embodiments of this application are shown in Table 1 below: Table 1

[0021] The unsaturated polyester resin, PMMA powder, zinc stearate, TBIC, TBHQ, BHT, calcium carbonate, aluminum hydroxide, and glass fiber used in this invention are all commercially available food contact grade raw materials and all meet the relevant standard requirements of GB 4806.7-2016.

[0022] The "low cost" mentioned in this invention means that, compared with traditional food contact grade BMC materials (costing about 9-10 yuan / kg), the material cost of this invention can be controlled below 7 yuan / kg, with a cost reduction of more than 30%.

[0023] The advantages of the BMC material of this invention are: 1. By using food-contact grade styrene-type unsaturated polyester resin, the cost of resin is reduced. Specifically, traditional food-contact grade BMC materials mostly use non-toxic active monomers such as methyl methacrylate and special active polyester resins that can react with methyl methacrylate. Due to the special nature of the raw materials, the price of such resins is high, with a unit price of about 25-35 yuan / kg. However, the low-cost food-contact grade BMC material of this invention uses common styrene-type active monomers and ordinary polyester resins that have passed food contact material testing. The unit price of the raw materials is about 10-15 yuan / kg. Calculated at an addition rate of 20%, the material cost can be reduced by about 3 yuan / kg.

[0024] Furthermore, traditional food-contact grade BMC materials have high resin costs, accounting for over 50% of the total cost. Adjusting the formula under processing constraints can cause cost fluctuations of 10-15%, which manufacturers find difficult to absorb. In contrast, the low-cost food-contact grade BMC material of this invention has resin costs accounting for approximately 30%, and formula adjustments only result in cost changes of about 3-8%. Moreover, because it uses styrene as an active diluent, the material's fluidity is far superior to traditional methods, making it easier to produce defect-free products.

[0025] 2. By using solvent-free, low-shrinkage additive PMMA powder, the total amount of styrene monomer in the BMC material system is significantly reduced, achieving the favorable conditions of low residue and low release. In the BMC material products prepared in Examples 1-3 of this invention, the migration amount of styrene monomer is less than 0.01 mg / kg (detection limit), which can be regarded as styrene residue-free.

[0026] 3. By using special curing agent TBIC and polymerization inhibitor TBHQ, and controlling the amount and ratio of TBIC curing agent and TBHQ polymerization inhibitor, the material can be cured quickly without any monomer residue.

[0027]

[0028] According to the formula comparison, the active monomer content in the new food contact grade BMC material formula is 5.6%, which is much lower than the active monomer content of 8.85% in the traditional food contact grade BMC material formula. This can effectively reduce the amount of active diluent added in BMC material, so that there is almost no active monomer residue after the BMC material is molded, and no harmful substances migrate after contact with food. The product meets the food contact grade standard.

[0029] In traditional BMC materials, the amounts of curing agent and polymerization inhibitor are less than 0.3%. This invention optimizes the amounts of curing agent and polymerization inhibitor, which can increase the reaction rate to more than twice that of traditional formulations, ensuring that the active monomers in the BMC material fully participate in the reaction.

[0030] Example 1

[0031] The preparation method is as follows:

[0032] The preparation methods for the following examples and comparative examples are the same as those in Example 1.

[0033] Example 2

[0034] Example 3

[0035] Comparative Example 1

[0036] Comparative Example 2

[0037] Comparative Example 3

[0038] Performance tests are as follows:

[0039]

[0040] From the above examples and comparative examples, we can see that: 1. Ordinary BMC materials cannot pass the test according to the requirements of GB 4806.7; 2. Although traditional food contact grade BMC materials can pass the test, they are expensive (9.93 yuan / kg) and can hardly replace common food contact grade plastics. 3. Comparative Example 3 shows that different ratios of curing agent TBIC to polymerization inhibitor TBHQ have a significant impact on sensory testing. In the total migration test, the value changes from ND to detectable, indicating that the ratio of curing agent to polymerization inhibitor has a significant impact on whether the product can meet food contact grade. The optimal ratio of curing agent TBIC to polymerization inhibitor TBHQ is between 4:1 and 6:1. 4. According to the three embodiments of the present invention, not only can it fully pass the test of GB4806.7, but it also performs better in terms of total migration and potassium permanganate consumption, and can also achieve V0 level flame retardancy. 5. According to the three embodiments of the present invention, the cost can be controlled below 7 yuan / kg, which can greatly expand the application field of food contact grade BMC materials.

[0041] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A BMC material for making a food contact article, characterized in that, The following components are included by mass percentage: 12%~20% food contact grade styrene-type unsaturated polyester resin, wherein the styrene-type unsaturated polyester resin meets the requirements of GB 4806.7-2016 standard; 3%~10% solvent-free polymethyl methacrylate (PMMA) powder; 0.5%~1% zinc stearate; 0.2%~0.6% of curing agent tert-butyl isopropyl peroxide (TBIC); 0.01%~0.1% of polymerization inhibitor tert-butylhydroquinone (TBHQ); 0.01%~0.05% of the stabilizer butylated hydroxytoluene (BHT); 20%~45% calcium carbonate; 10%~40% aluminum hydroxide; 5%~10% glass fiber; The sum of the above components is 100%.

2. A BMC material for making a food contact article according to claim 1, wherein, The following components are included by mass percentage: 15.18% food contact grade styrene-based unsaturated polyester resin, 4.28% solvent-free polymethyl methacrylate (PMMA) powder; 0.93% zinc stearate; 0.39% curing agent TBIC; 0.08% of polymerization inhibitor TBHQ; 0.02% stabilizer BHT; 42.8% calcium carbonate; 29.18% aluminum hydroxide; 7.14% glass fiber.

3. A BMC material for preparing food contact articles according to claim 1 or 2, characterized in that, The amount of styrene monomer migration in the cured product is less than 0.01 mg / kg.

4. A low-cost BMC material for preparing food contact articles according to claim 1 or 2, characterized in that, The ratio of curing agent TBIC to polymerization inhibitor TBHQ is between 4:1 and 6:

1.

5. A method for preparing a BMC material for use in food contact articles as described in any one of claims 1-4, characterized in that, Includes the following steps: S1 involves adding unsaturated polyester resin, low-shrinkage additives, mold release agents, curing agents, polymerization inhibitors, stabilizers, etc., into a high-speed disperser and mixing them to obtain a resin liquid. S2 adds calcium carbonate powder and aluminum hydroxide powder to a kneader and kneads them to obtain a mixed powder. S3 mixes the resin liquid with the mixed powder in a kneader to obtain a resin paste; S4 then adds glass fiber to the kneader containing the resin paste, kneads it, and obtains BMC material.

6. The preparation method according to claim 5, characterized in that: After step S4, step S5 involves removing the BMC material from the kneader, bagging and packaging it to obtain the finished product.

7. The preparation method according to claim 5, characterized in that: The mixing time in S1 is 15-25 minutes; the kneading time in S2 is 15-25 minutes.

8. The preparation method according to claim 5, characterized in that: The kneading time in S3 is 15-25 minutes.

9. The preparation method according to claim 5, characterized in that: The kneading time in S4 is 8-12 minutes.

10. The application of the BMC material according to any one of claims 1-4 in the preparation of food contact articles, wherein the food contact articles include one or more of tableware, kitchen utensils, food processing equipment parts, and food packaging containers.

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