JP2015000121A - Melamine resin composition for microwave-safe tableware - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a melamine resin composition for microwave-safe tableware, which is excellent particularly in properness for high-frequency waves of a microwave oven and which satisfies overall characteristics required for the microwave-safe tableware.SOLUTION: A melamine resin composition for microwave-safe tableware contains a melamine resin and a reinforcement material. The melamine resin composition contains 4-35 mass% of the highly-tough melamine resin with respect to the whole quantity of the composition as a resin component, and contains 7-35 mass% of a polytetrafluoroethylene resin with respect to the whole quantity of the composition as the reinforcement material.

Description

  The present invention relates to a melamine resin composition used as a molding material for producing tableware that can be heated by a microwave oven.

  In producing food containers for use in microwave ovens, pottery and polyethylene terephthalate (PET) resin are used as typical materials. However, pottery tends to be damaged, and PET resin molding materials have disadvantages that it is difficult to color.

  On the other hand, a melamine resin is known as a material that does not have the above-described drawbacks. This molding material has high hardness and can be colored freely, and is excellent in water resistance and chemical resistance, and can be suitably used for tableware.

  Conventionally, what mixed powder pulp as a reinforcing material has been used as a melamine resin molding material for manufacturing tableware (patent document 1).

  In addition, Patent Document 2 proposes a technique using cotton powder as a reinforcing material instead of powder pulp.

JP 2000-129083 A Japanese Patent No. 3815346

  However, since the tableware molded from the conventional melamine resin molding material has a high ratio of melamine resin (for example, 70 to 75% by mass), heat resistance is insufficient, durability against heating in a microwave oven is low, and cracks are generated. May occur.

  Therefore, it is conceivable to increase the amount of powdered pulp and reduce the ratio of melamine resin, but the powdered pulp itself easily absorbs moisture, and when heated in a microwave oven, this moisture is heated and evaporated, and on the other hand, cracks are generated. This will happen.

  In Patent Document 2, attempts are made to solve these problems by using cotton powder. However, there is a demand for a novel material that satisfies overall characteristics including durability, such as microwave high-frequency suitability. .

  The present invention has been made in view of the circumstances as described above. In particular, the melamine for dishware for microwave ovens is excellent in microwave high frequency suitability and satisfies the overall characteristics required for microwave oven tableware. It is an object to provide a resin composition.

  In order to solve the above-mentioned problems, the melamine resin composition for tableware for microwave ovens of the present invention is a melamine resin composition for tableware for microwave ovens containing a melamine resin and a reinforcing material. 4 to 35% by mass of a high-toughness melamine resin and 7 to 35% by mass of a polytetrafluoroethylene resin as a reinforcing material with respect to the total amount of the composition.

  According to the melamine resin composition for tableware for microwave ovens of the present invention, it is possible to satisfy the overall characteristics required for tableware for microwave ovens.

  The present invention is described in detail below.

  Although it does not specifically limit as a melamine resin used for the melamine resin composition for tableware of this invention, For example, a methylolation melamine resin, a methylolation melamine-phenol cocondensation resin, a methylolation melamine- Synthetic resins obtained by cocondensation of triazines and formaldehydes such as urea co-condensation resins and methylolated melamine-epoxy co-condensation resins can be used. Specifically, powdered melamine formaldehyde condensation polymerization resin (such as “CP9012” manufactured by Panasonic Corporation) can be used.

  The content of the melamine resin is preferably in the range of 7 to 50% by mass with respect to the total amount of the melamine resin composition for tableware for microwave ovens. Within this range, the content of unreacted melamine resin remaining in the molded product can be reduced, and it becomes possible to suppress the generation of condensed water when this molded product is heated by a microwave oven. The occurrence of cracks due to condensed water can be prevented.

  The melamine resin composition for tableware according to the present invention contains a high toughness melamine resin as a resin component. By blending a high toughness melamine resin, the microwave high frequency suitability can be improved. In particular, blending polytetrafluoroethylene resin improves microwave high-frequency suitability, heat resistance, microwave oven durability, etc., and blending high-toughness melamine resin further increases microwave microwave suitability. It is improved, the moldability of the molded product is satisfactory, and problems of odor, taste and color do not occur.

  The tough melamine resin is a resin obtained by reacting in a neutral or weak alkali under the condition of a molar ratio (F / M) of melamine (M) to formaldehyde (F) of 1.5 to 1.7. is there. Specifically, “high toughness melamine resin” manufactured by Panasonic Corporation can be used.

  Content of a high toughness melamine resin exists in the range of 4-35 mass% with respect to the whole quantity of the melamine resin composition for tableware corresponding to a microwave oven. Within this range, the microwave oven high frequency suitability can be improved, the moldability of the molded product is satisfactory, and problems of odor, taste and color do not occur.

  In the present invention, polytetrafluoroethylene resin is blended as the reinforcing material. By blending the polytetrafluoroethylene resin, the microwave oven high frequency suitability can be greatly improved. In addition, heat resistance, microwave oven durability, etc. are improved.

The polytetrafluoroethylene resin is not particularly limited. For example, a powder having an average particle diameter of 20 to 50 μm and a melt viscosity of 10 ¹⁰ to 10 ¹¹ poise (380 ° C.) can be used.

  Content of polytetrafluoroethylene resin exists in the range of 7-35 mass% with respect to the whole quantity of the melamine resin composition for tableware corresponding to a microwave oven. Within this range, the microwave high frequency suitability can be greatly improved, and the heat resistance, microwave durability and the like are also improved.

  The melamine resin composition for tableware for the microwave oven of the present invention can further contain other components within the range not impairing the effects of the present invention. Examples of such other components include organic fillers such as melamine pulverized products, inorganic fillers such as barium sulfate, curing agents such as phthalic anhydride, stearic acid, zinc stearate, montanic acid, and carboxyl group-containing polyolefins. And a release agent such as a plasticizer and a colorant.

  The melamine resin composition for tableware according to the present invention can be prepared as follows. First, the above melamine resin, the reinforcing material, and other components are blended, and this is uniformly pulverized and mixed with a ball mill. Next, the mixture is formed into a sheet using a roll, and the obtained sheet is pulverized to prepare a granular melamine resin composition for tableware corresponding to a microwave oven. Alternatively, the mixture can be heated and kneaded with a kneader or a roll and then solidified by cooling, and the solidified product obtained can be pulverized to prepare a powdery melamine resin composition for microwave oven-compatible dishes.

  By molding the melamine resin composition for tableware prepared as described above by a method such as compression molding, tableware that can be heated by a microwave oven can be manufactured.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples. In addition, the compounding quantity shown in Table 1 represents a mass part.

  By crushing melamine resin (melamine formaldehyde condensation polymerization resin, "CP9012" manufactured by Panasonic Corporation), organic filler (melamine pulverized product, molded product of melamine resin molding material, runner, spool, molding burr generated during molding Prepared), high toughness melamine resin (Panasonic Corporation "high toughness melamine resin"), PTFE resin (Daikin Kogyo Co., Ltd. "Polyflon powder"), barium sulfate (Sakai Chemical Industry Co., Ltd.) , A curing agent (phthalic anhydride, manufactured by Toho Chemical Co., Ltd.), a mold release agent (zinc stearate), and a plasticizer are blended in the blending amounts shown in Table 1, and this is uniformly pulverized with a ball mill for 2 hours. Mixed.

  In Comparative Example 1, no PTFE resin was blended, and in Comparative Example 3, a high toughness melamine resin was not blended.

  Next, the mixture was heated and kneaded with a kneader and then solidified by cooling, and the solidified product was pulverized to a predetermined particle size with a pulverizer to prepare melamine resin compositions for dishes for microwave ovens of Examples and Comparative Examples. .

  Then, a dish having a diameter of 120 mm is manufactured as a molded product by compression molding the melamine resin composition for tableware corresponding to a microwave oven under the conditions of a temperature of 160 ° C., a pressure of 20 MPa, and a molding time of 90 minutes, and this dish is used as a test for evaluation. It was a piece.

  At the time of molding, the moldability of the melamine resin composition for dishware for microwave ovens was evaluated with `` ○ '' indicating that no abnormality was observed in the appearance and `` X '' indicating that the appearance abnormality was not filled, etc. . The results are shown in Table 1. Only the comparative example 2 which mix | blended PTFE resin in a large quantity was not able to shape | mold said dish.

Next, the following tests prescribed in JIS S 2033 were performed on the test pieces for evaluation of Examples and Comparative Examples. The results of each test are shown in Table 1.
(Microwave high frequency suitability)
The operation of putting the test piece for evaluation into a microwave oven, heating it for 2 minutes at a rated high frequency output of 1000 W, taking it out and allowing it to cool to 23 ± 5 ° C. was repeated. And the external appearance of the test piece for evaluation after a test was observed visually, and the presence or absence of a crack and discoloration was investigated. In Table 1, regarding the discoloration of the appearance, “◯” indicates that no crack or discoloration was observed on the surface of the test piece for evaluation, and “×” indicates that the crack was observed.
(Heat-resistant)
Put the test piece for evaluation placed at the center of the slate plate in the thermostatic chamber with an air agitator set in advance at 140 ± 3 ° C together with the slate plate, hold it for 1 hour, take it out with the slate plate, and leave it as it is. It was allowed to cool to ± 5 ° C. And the external appearance of the test piece for evaluation after a test was observed visually, and the presence or absence of abnormality and discoloration was investigated. In the heat resistance column of Table 1, there are shown temperatures at which abnormalities such as discoloration, which are disadvantages in use, are observed.
(Impact resistance)
The test piece for evaluation is placed on a plaster board having a thickness of 3 cm or more placed almost horizontally on a flat concrete floor, and the steel ball is dropped from a height of 20 to 30 cm toward the center of the test piece for evaluation. Thus, it was investigated whether breakage or the like was damaged. The impact resistance column in Table 1 shows the drop height at which breakage occurs.
(Durability of microwave oven)
(A) A predetermined olive oil is filled to about 50% of the capacity of the test piece for evaluation, and heated using a microwave oven to 160 ° C.
(B) When the olive oil reaches a predetermined temperature according to (a), the evaluation test piece is taken out of the microwave oven, and immediately put into a low-temperature bath set at −40 ± 3 ° C. and cooled to the predetermined temperature.
(C) The operations of (a) and (b) were repeated 5 times. However, after the second time, the operations of (a) and (b) were repeated from the state cooled by (b).

And after operation of (a)-(c), the external appearance of the test piece for evaluation was observed by visual observation, and the presence or absence of abnormalities such as breakage and discoloration, which became defects in use, was examined. In the column of the number of cycles in Table 1, the number of repetitions of the above operation in which an abnormality such as breakage is observed is shown. Regarding the discoloration of the appearance, “○” indicates that the discoloration is grade 3 or more, discoloration "X" indicates that is less than 3rd grade.
(Odor, taste, color)
The odor and taste were inspected based on the JIS S 2033 method. The color inspection was performed visually.

  The evaluation results are shown in Table 1.

  From Table 1, Examples 1-7 which mix | blended high-toughness melamine resin as a resin component, and mix | blended polytetrafluoroethylene resin as a reinforcing material are excellent in microwave oven high frequency suitability, and are requested | required by the other microwave oven corresponding tableware. The overall characteristics were also satisfactory.

  In particular, by blending polytetrafluoroethylene resin, the microwave high frequency suitability can be greatly improved, and heat resistance, microwave oven durability and the like have also been improved. When a high-toughness melamine resin was used in combination, the microwave high-frequency suitability was further improved, and the moldability, odor, taste and color were not impaired.

Claims (1)

  In the melamine resin composition for dishware for microwave ovens containing a melamine resin and a reinforcing material, the resin component contains a high toughness melamine resin of 4 to 35% by mass relative to the total amount of the composition, and the reinforcing material has a total amount of the composition. 7-35 mass% polytetrafluoroethylene resin is contained with respect to the microwave oven-compatible tableware melamine resin composition characterized by the above-mentioned.