Antibacterial melamine resin tableware and preparation method thereof

Abstract

The present invention relates to the technical field of plastic products, specifically discloses a kind of antibacterial melamine resin tableware and preparation method thereof, specifically including the following steps: S1, preheated melamine mixture is added into melamine mold for compression molding, during which the upper and lower pressing exhausts 1-5 times; S2, after brushing liquid melamine formaldehyde resin on the back of flower paper, the preheated color-changing powder is sprayed, and then attached to the preset position of the melamine tableware main body surface in the melamine mold, mold closing compression molding, during which the upper and lower pressing exhausts 1-5 times; S3, antibacterial varnish powder is evenly sprinkled on the surface of melamine tableware with flower paper, and mold closing compression molding. The present invention has excellent antibacterial performance and color change temperature indication function, and the formaldehyde migration amount can be controlled within 1mg / kg, which meets the provisions of "National Food Safety Standard Food Contact Plastic Materials and Products" and "Antibacterial Property Determination Method and Antibacterial Effect of Antibacterial Coating (Paint Film)".

Description

Technical Field

[0001] The invention relates to the technical field of plastic products, and in particular to antibacterial melamine resin tableware and a preparation method thereof. Background Art

[0002] Melamine resin is a new type of thermosetting plastic made of melamine formaldehyde resin as the base material, adding wood pulp cellulose, curing agent and other additives. It is widely used in making tableware, electrical components, sanitary ware, house decoration materials, etc. Melamine tableware has a ceramic-like luster and is called imitation porcelain tableware. This kind of imitation porcelain tableware has the advantages of light weight, not easy to break, and beautiful appearance.

[0003] Melamine tableware is a plastic product that comes into direct contact with food. The National Food Safety Standard for Plastic Materials and Products for Food Contact (GB4806.7-2016) sets a limit on the amount of formaldehyde migration. The source of formaldehyde is mainly the residue of the main ingredient melamine formaldehyde resin during the preparation process and the decomposition during the pressing process. For the residual formaldehyde in the resin, formaldehyde capture agents (such as hydrogen peroxide, thiourea, etc.) are generally added during the synthesis process to reduce the free formaldehyde content, or modifiers (such as small molecule alcohols) are added to block the hydroxymethyl group, reduce its activity and further prevent intermolecular condensation. However, in addition to being discharged, some of the formaldehyde generated during the processing of melamine powder pressed into tableware is also retained in the tableware, which leads to excessive formaldehyde migration. In addition, there are also requirements for the antibacterial and hygienic properties of melamine tableware, and the use temperature is also limited. The current melamine tableware does not have a color-changing temperature indication function. Summary of the invention

[0004] The object of the present invention is to provide an antibacterial melamine resin tableware and a preparation method thereof, which has excellent antibacterial performance and color-changing temperature indication function, and the formaldehyde migration amount can be controlled within 1 mg / kg.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is:

[0006] A method for preparing antibacterial melamine resin tableware, comprising the following steps:

[0007] S1. The preheated melamine mixture is added into a melamine mold for pressing and molding at a temperature of 145°C-165°C, a pressure of 15MPa-25MPa, and a time of 1min-3min. During the pressing and molding, the melamine tableware body is obtained by pressing and venting 1-5 times.

[0008] S2, brushing liquid melamine formaldehyde resin on the back of the flower paper and then spraying preheated color-changing powder, and then sticking it on the preset position on the surface of the melamine tableware body in the melamine mold, closing the mold and pressing it, the temperature is 145℃-165℃, the pressure is 10MPa-15MPa, the time is 30 seconds-60 seconds, during which the upper and lower pressing and exhausting are performed 1-5 times, and the melamine tableware with flower paper is obtained;

[0009] S3. Sprinkle the antibacterial glazing powder evenly on the surface of the melamine tableware with flower paper, close the mold and press it into shape at a temperature of 145°C-165°C, a pressure of 15MPa-20MPa, and a time of 20 seconds-30 seconds. During this period, press and exhaust 1-3 times, open the mold, grind the edges, and polish to obtain the antibacterial melamine resin tableware.

[0010] Preferably, the preheating temperature of the melamine mixture in step S1 is 70° C.-90° C., and the preheating time is 30 seconds-60 seconds.

[0011] Preferably, the melamine mixture in step S1 comprises the following components in parts by weight: 100 parts of melamine resin powder, 15-25 parts of α-wood pulp fibers, 5-10 parts of nanocrystalline cellulose particles, 1-5 parts of lubricant, and 0.5-2 parts of curing agent.

[0012] Preferably, the pH value of the liquid melamine formaldehyde resin in step S2 is adjusted to 8-9.

[0013] Preferably, the color-changing powder in step S2 is a modified melamine resin powder mixture, which contains a peptide-modified melamine having a peptide side chain in the molecular chain, and its structural formula is:

[0014] .

[0015] Preferably, the preparation method of the modified melamine resin powder mixture is:

[0016] S21, taking trimethylolmelamine and methanol into a reaction kettle, adding acid to adjust the pH value to 3-4, the temperature to 40°C-50°C, stirring and reacting for 90min-120min; then adding alkali to adjust the pH value to 7.5-8.0, stirring and neutralizing, distilling and removing, cooling and filtering to obtain methyl etherified melamine;

[0017] S22, adding 1,11-undecanediol to methyl etherified melamine at a molar ratio of 1:1, stirring and heating to 110° C.-130° C. to carry out an ether exchange reaction, and after the reaction is completed, removing methanol by distillation to obtain an intermediate mixture;

[0018] S23, dissolving the intermediate mixture in a solvent and adding toluene-4-sulfonic acid and polylauryl glutamic acid to carry out ester exchange reaction and condense and reflux, and after the reaction is completed, precipitate and spray dry to obtain a modified melamine resin powder mixture.

[0019] Preferably, the structural formula of the polylauryl glutamate is:

[0020] .

[0021] Preferably, the antibacterial glazing powder in step S3 comprises the following components in parts by weight: 100 parts of glazing powder, 1.5-3.5 parts of nano titanium dioxide, 1.5-3 parts of dispersant, 0.2-0.5 parts of coupling agent and 0.3-0.5 parts of lubricant.

[0022] Preferably, the glazing powder is LG110 type, LG220 type or LG250 type.

[0023] The invention also provides antibacterial melamine resin tableware prepared by the preparation method.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The melamine resin tableware of the present invention comprises a melamine tableware main body and a flower paper and an antibacterial glazing powder on its surface. The nano titanium dioxide in the antibacterial glazing powder can kill various bacteria on the surface of the tableware in a short time, and the antibacterial effect is long-lasting. The antibacterial effect test of Escherichia coli and Staphylococcus aureus is carried out in accordance with GB / T21866-2008 "Determination of antibacterial properties and antibacterial effects of antibacterial coatings (paint films)".

[0026] In addition, nanocrystalline cellulose particles are added to the body of the melamine resin tableware of the present invention, which has physical and chemical adsorption effects on formaldehyde generated during the molding process, and can further consume formaldehyde during high-temperature processing, effectively reducing free formaldehyde; furthermore, pressing up and down during the pressing process helps to discharge formaldehyde in time; secondly, the color-changing powder between the flower paper and the body, on the one hand, utilizes the cholesteric liquid crystal phase property of the polylauryl glutamic acid side chain contained in the color-changing powder, which changes its pitch with the temperature, and changes the original color after the tableware temperature reaches a certain temperature, thereby achieving the color-changing temperature indication function, and on the other hand, the amino group in the color-changing powder reacts with free formaldehyde to effectively reduce free formaldehyde. The melamine tableware of the present invention complies with the provisions of the "National Food Safety Standard for Plastic Materials and Products for Food Contact" (GB4806.7-2016), and can be controlled within 1 mg / kg. DETAILED DESCRIPTION

[0027] Example 1

[0028] This embodiment provides a method for preparing antibacterial melamine resin tableware, which specifically comprises the following steps:

[0029] S1. The melamine mixture preheated at 80°C for 30 seconds is added into a melamine mold for pressing and molding at a temperature of 165°C, a pressure of 18 MPa, and a time of 2 minutes. During the pressing and exhausting, the melamine tableware body is obtained. The melamine mixture includes the following components in parts by weight: 100 parts of melamine resin powder, 20 parts of α-wood pulp fiber, 8 parts of nanocrystalline cellulose particles, 3.5 parts of zinc stearate, and 1 part of amide amine curing agent.

[0030] S2. The back of the flower paper is coated with liquid melamine formaldehyde resin with a pH value of 8.5 and then sprayed with preheated color-changing powder. The paper is then attached to a preset position on the surface of the melamine tableware body in the melamine mold. The mold is closed and pressed into shape at a temperature of 150° C. and a pressure of 12 MPa for 45 seconds. During the pressing and exhausting, the paper is pressed up and down twice to obtain melamine tableware with flower paper.

[0031] S3, the antibacterial glazing powder is evenly sprinkled on the surface of the melamine tableware with flower paper, and the mold is pressed and formed at a temperature of 165°C, a pressure of 20MPa, and a time of 30 seconds. During the pressing and exhausting, the mold is opened, the edges are ground, and the antibacterial melamine resin tableware is obtained. The antibacterial glazing powder includes the following components in parts by weight: 100 parts of LG110 type glazing powder, 3.5 parts of nano titanium dioxide, 2 parts of ethylene bis stearic acid amide, 0.35 parts of silane coupling agent and 0.5 parts of zinc stearate.

[0032] The color-changing powder in step S2 is a modified melamine resin powder mixture, and its preparation method is as follows: S21, trimethylol melamine and methanol are added to a reactor in a molar ratio of 1:5, acid is added to adjust the pH value to 4, the temperature is 50°C, and the reaction is stirred for 120 minutes; then alkali is added to adjust the pH value to 8.0, and after stirring and neutralization, methanol, formaldehyde, and water are removed by distillation at a vacuum degree of 0.1MPa and a temperature of 110°C, and cooled and filtered to obtain methylated melamine. S22, 1,11-undecanediol is added to the methylated melamine in a molar ratio of 1:1, and the temperature is stirred and heated to 125°C for ether exchange reaction. After the reaction is completed, methanol is removed by distillation to obtain an intermediate mixture. S23, the intermediate mixture is dissolved in a methanol solvent and toluene-4-sulfonic acid and polylauryl glutamic acid are added for ester exchange reaction, heated and stirred at a temperature of 80°C and condensed and refluxed, and precipitated after the reaction is completed, and spray-dried to obtain a modified melamine resin powder mixture.

[0033] The melamine resin tableware prepared in Example 1 has a formaldehyde migration amount of 0.82 mg / kg tested in accordance with GB4806.7-2016, and an antibacterial rate of Staphylococcus aureus of more than 95% and an antibacterial rate of Escherichia coli of more than 99% tested in accordance with GB / T21866-2008.

[0034] Example 2

[0035] This embodiment provides a method for preparing antibacterial melamine resin tableware, which specifically comprises the following steps:

[0036] S1. The melamine mixture preheated at 80°C for 45 seconds is added into a melamine mold for pressing and molding at a temperature of 155°C, a pressure of 20 MPa, and a time of 2 minutes. During the pressing and exhausting, the melamine tableware body is obtained. The melamine mixture includes the following components in parts by weight: 100 parts of melamine resin powder, 25 parts of α-wood pulp fiber, 10 parts of nanocrystalline cellulose particles, 5 parts of zinc stearate, and 1 part of amidoamine curing agent.

[0037] S2. The back of the flower paper is coated with liquid melamine formaldehyde resin with a pH value of 9 and then sprayed with preheated color-changing powder. The paper is then attached to a preset position on the surface of the melamine tableware body in the melamine mold. The mold is closed and pressed into shape at a temperature of 150° C. and a pressure of 15 MPa for 30 seconds. During the pressing and exhausting, the paper is pressed up and down twice to obtain melamine tableware with flower paper.

[0038] S3, the antibacterial glazing powder is evenly sprinkled on the surface of the melamine tableware with flower paper, and the mold is pressed and formed at a temperature of 155°C, a pressure of 22MPa, and a time of 20 seconds. During the pressing and exhausting, the mold is opened, the edges are ground, and the antibacterial melamine resin tableware is obtained. The antibacterial glazing powder includes the following components in parts by weight: 100 parts of LG220 type glazing powder, 3 parts of nano titanium dioxide, 1.5 parts of ethylene bis stearic acid amide, 0.25 parts of silane coupling agent and 0.4 parts of zinc stearate.

[0039] The color-changing powder in step S2 is a modified melamine resin powder mixture, and its preparation method is as follows: S21, take trimethylol melamine and methanol in a molar ratio of 1:6 and add them to a reactor, add acid to adjust the pH value to 3.5, the temperature is 45°C, and stir to react for 120 minutes; then add alkali to adjust the pH value to 7.5, stir and neutralize, distill and remove methanol, formaldehyde, and water at a vacuum degree of 0.1MPa and a temperature of 105°C, and cool and filter to obtain methylated melamine. S22, add 1,11-undecanediol to the methylated melamine in a molar ratio of 1:1, stir and heat to 125°C for ether exchange reaction, and distill and remove methanol after the reaction is completed to obtain an intermediate mixture. S23, dissolve the intermediate mixture in a methanol solvent and add toluene-4-sulfonic acid and polylauryl glutamic acid for ester exchange reaction, heat and stir at a temperature of 75°C and condense and reflux, precipitate after the reaction is completed, and spray dry to obtain a modified melamine resin powder mixture.

[0040] The melamine resin tableware prepared in Example 2 has a formaldehyde migration amount of 0.85 mg / kg according to the test of GB4806.7-2016, and an antibacterial rate of Staphylococcus aureus of more than 95% and an antibacterial rate of Escherichia coli of more than 99% according to the test of GB / T21866-2008.

[0041] The structural formula of the polylauryl glutamate in the above-mentioned embodiments 1 and 2 is:

[0042] .

[0043] The modified melamine resin powder mixture in the above-mentioned Examples 1 and 2 contains a peptide-modified melamine having a peptide side chain in the molecular chain, and its structural formula is:

[0044] .

[0045] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which shall fall within the scope of the present invention to be protected. The scope of protection of the present invention shall be defined by the attached claims and their equivalents.

Claims

1. A method for preparing antibacterial melamine resin tableware, characterized in that: The specific steps include: S1. The preheated melamine mixture is added into a melamine mold for pressing and molding at a temperature of 145°C-165°C, a pressure of 15MPa-25MPa, and a time of 1min-3min. During the pressing and molding, the melamine tableware body is obtained by pressing and venting 1-5 times. S2, brushing liquid melamine formaldehyde resin on the back of the flower paper and then spraying preheated color-changing powder, and then sticking it on the preset position on the surface of the melamine tableware body in the melamine mold, closing the mold and pressing it, the temperature is 145℃-165℃, the pressure is 10MPa-15MPa, the time is 30 seconds-60 seconds, during which the upper and lower pressing and exhausting are performed 1-5 times, and the melamine tableware with flower paper is obtained; S3, evenly sprinkle the antibacterial glazing powder on the surface of the melamine tableware with flower paper, close the mold and press it into shape, the temperature is 145℃-165℃, the pressure is 15MPa-20MPa, and the time is 20 seconds-30 seconds. During this period, press and exhaust 1-3 times, open the mold, grind the edges, and polish to obtain the antibacterial melamine resin tableware; The color-changing powder in step S2 is a modified melamine resin powder mixture, which contains a peptide-modified melamine having a peptide side chain in the molecular chain, and its structural formula is: ； The preparation method of the modified melamine resin powder mixture is: S21, taking trimethylolmelamine and methanol into a reaction kettle, adding acid to adjust the pH value to 3-4, the temperature to 40°C-50°C, stirring and reacting for 90min-120min; then adding alkali to adjust the pH value to 7.5-8.0, stirring and neutralizing, distilling and removing, cooling and filtering to obtain methylated trimethylolmelamine; S22, adding 1,11-undecanediol to methylated trimethylolmelamine at a molar ratio of 1:1, stirring and heating to 110° C.-130° C. to carry out an ether exchange reaction, and after the reaction is completed, removing methanol by distillation to obtain an intermediate mixture; S23, dissolving the intermediate mixture in a solvent and adding toluene-4-sulfonic acid and polylauryl glutamate to carry out an ester exchange reaction and condense and reflux, and after the reaction is completed, precipitate and spray dry to obtain a modified melamine resin powder mixture; The structural formula of the polylauryl glutamate is: 。 2. The method for preparing antibacterial melamine resin tableware according to claim 1, characterized in that: The preheating temperature of the melamine mixture in step S1 is 70° C.-90° C., and the preheating time is 30 seconds-60 seconds.

3. The method for preparing antibacterial melamine resin tableware according to claim 1, characterized in that: The melamine mixture in step S1 comprises the following components in parts by weight: 100 parts of melamine resin powder, 15-25 parts of α-wood pulp fibers, 5-10 parts of nanocrystalline cellulose particles, 1-5 parts of lubricant, and 0.5-2 parts of curing agent.

4. The method for preparing antibacterial melamine resin tableware according to claim 1, characterized in that: The pH value of the liquid melamine formaldehyde resin in step S2 is adjusted to 8-9.

5. The method for preparing antibacterial melamine resin tableware according to claim 1, characterized in that: The antibacterial glazing powder in step S3 comprises the following components in parts by weight: 100 parts of glazing powder, 1.5-3.5 parts of nano titanium dioxide, 1.5-3 parts of dispersant, 0.2-0.5 parts of coupling agent and 0.3-0.5 parts of lubricant.

6. The method for preparing antibacterial melamine resin tableware according to claim 5, characterized in that: The glazing powder is of LG110 type, LG220 type or LG250 type.

7. Antibacterial melamine resin tableware prepared by the preparation method according to any one of claims 1 to 6.

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