JP2003119693A - Paper-converting agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper-converting agent giving paper containers, such as food packages, which have excellent steam resistance, can resist to the heat of microwave ovens or the like, and can be composted together with foods. SOLUTION: This paper-converting agent comprising a biodegradable resin emulsion and used for forming water-resistant coating films on paper is characterized in that the biodegradable resin emulsion is obtained by emulsifying a polyester-based biodegradable resin having a melting point of >=130 deg.C with an emulsifier, wherein the carboxylic acid in the resin is neutralized with an alkaline substance.

Description

Description: TECHNICAL FIELD The present invention relates to a paper processing agent,
The present invention relates to a paper processing agent used for forming a water-resistant coating on paper, which is a material of paper products such as food packages. [0002] Paper food packages are inexpensive and can be composted, so they are positioned as one of important materials in the future resource recycling society. [0003] However, food packages are required to have sufficient water resistance, and those expected to be heated by a microwave oven or the like also need not be deformed or permeated by generated steam. Is done. For this reason, paper coated with polyethylene has been mainly used as a conventional food packaging material, but since the polyethylene is not biodegradable, the food package could not be composted with the food. However, the recycling of food waste has been institutionalized by the Food Recycling Law from the spring of 2001, and the separation and disposal of lunches represented by convenience stores has become a major problem in terms of cost. Therefore, in order to obtain a paper food package that can be composted with food, a coating material that replaces polyethylene is required. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a paper container such as a food package that can withstand heating by a microwave oven or the like and that can be composted with food. It is an object to provide a paper processing agent that can be used. [0006] The paper processing agent of claim 1 is:
A paper processing agent comprising a biodegradable resin emulsion and forming a water-resistant film on paper. In order to solve the above-mentioned problems, the biodegradable resin emulsion is a polyester-based biodegradable resin having a melting point of 130 ° C. or more. Is emulsified with an emulsifier,
It is assumed that the carboxylic acid in the resin is a resin emulsion neutralized with an alkaline substance. DETAILED DESCRIPTION OF THE INVENTION The polyester-based biodegradable resin emulsion used in the present invention is obtained by emulsifying a polyester-based biodegradable resin with an emulsifier, and the carboxylic acid contained in the resin is an alkali substance. It is a sum. The polyester-based biodegradable resin is a conventionally used biodegradable polyester-based polymer compound, and may contain residual (unreacted) monomers and / or oligomers. Oligomers,
Or those having a carboxyl group at the terminal of the polymer. However, a resin having a melting point of 130 ° C. or higher is selected in order to prevent the paper product obtained by the processing of the paper processing agent from being deformed or permeated by water vapor generated when heated by a microwave oven or the like. Specific examples include lactic acid, hydroxybutyric acid,
Examples include hydroxyalkanoic acids such as hydroxyvaleric acid, malic acid, and glycolic acid, and homopolymers of ε-caprolactone, and copolymers thereof. [0010] Further, the terminal carboxylic acid copolymer of succinic acid and ethylene glycol and / or butylene glycol, and the terminal monomers of succinic acid and ethylene glycol and / or butylene glycol containing these residual monomers and oligomerized carboxylic acid terminals. Alcohol copolymers can also be used. Examples of the alkaline substance for neutralizing the carboxylic acid in the polyester biodegradable resin as described above include common alkaline substances such as sodium hydroxide, sodium carbonate, aqueous ammonia, triethylamine and triethanolamine. However, amino saccharides are preferably used from the viewpoint of high safety, and examples thereof include modified saccharides / polysaccharides such as amine-modified carboxymethylcellulose and 2-amino-β-D-glucopyranoside. Saccharides may be mentioned, among which D-glucosamine,
Biologically derived biomass amines such as D-galactosamine and chitosan are preferably used. By neutralizing the carboxylic acid in the resin with these alkaline substances, the storage stability of the paper processing agent can be improved. Next, the emulsifier used in the present invention preferably contains a nonionic surfactant in an amount of 20 to 100% by weight, more preferably 50 to 100% by weight.
By using an emulsifier containing a nonionic surfactant in a specific amount or more, the pH in an aqueous state can be stably maintained at 4 to 7, and the storage stability of the paper processing agent is more excellent. It will be. Further, the nonionic surfactant preferably has a low molecular weight, and the molecular weight (Mw) is preferably 3000 or less, more preferably 1500 or less. Conventionally, there has been a problem such as the occurrence of problems due to the bleeding out of the surfactant over time on the surface of the coating film.However, by using a low molecular weight emulsifier, most of the surfactant is transferred to the surface when the emulsion is dried. Can be removed by one-time washing with water, so that it is possible to obtain a coating excellent in water resistance and containing almost no impurities. Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl amine ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan. Examples include fatty acid esters and sucrose fatty acid esters. Among them, polyoxyethylene lauryl ether and polyoxyethylene sorbitan fatty acid ester are preferred. In the emulsifier used in the present invention, in addition to the above-mentioned nonionic surfactant, anionic, cationic and
Alternatively, various amphoteric ionic surfactants can be used. Examples of the anionic surfactant include alkyl sulfate, polyoxyethylene alkyl ether sulfate, sulfosuccinate, N-acyl amino acid salt, carboxylate, sulfonate, phosphate and the like. . Examples of cationic surfactants include alkyl ammonium salts, and examples of amphoteric surfactants include alkyl (amide) betaine and alkyl dimethyl amine oxide. The amount of the emulsifier used is usually from 0.2 to 20 parts by weight based on 100 parts by weight of the polyester-based biodegradable resin.
Parts by weight (however, based on solid content). The specific method for emulsifying the polyester-based biodegradable resin using an emulsifier is not particularly limited, and a conventionally used general emulsification method can be employed. For example, a polyester-based biodegradable resin is
A method of dissolving this in a solvent that can dissolve it, adding an emulsifier, and then gradually adding water is used. Here, as the solvent, for example, ketone solvents such as butanone, ester solvents such as ethyl acetate, aromatic solvents such as toluene, and chlorine solvents such as dichloromethane can be used. Alternatively, after dissolving the polyester-based biodegradable resin in the above-mentioned solvent, an aqueous solution of an emulsifier is added to reach the phase inversion point at a stretch, and then diluted with water. Temperature to the melting temperature,
After mixing the emulsifier, a method of emulsifying by adding warm water can also be used. The paper processing agent of the present invention may contain a water repellent, a surface smoothing agent, a release agent, a thickener, a fluidity adjuster, a defoaming agent, a filler, a colorant, Additives such as an agent, a water retention agent, a preservative, an antioxidant, a light stabilizer, a cross-linking agent and the like can be contained. Various resin emulsions currently on the market can also be blended within a range not contrary to the object of the present invention. By applying the above-mentioned paper processing agent of the present invention to paper, it is possible to form a high-quality water-resistant coating excellent in biodegradability and containing almost no impurities. The coating method is not particularly limited, and a general coating method such as coating with various coaters, brush coating, spray coating, immersion and the like is appropriately used. After the application, it may be dried by a known method. However, the heating temperature is not more than the melting point of the used polyester biodegradable resin. The amount of the biodegradable resin applied to the paper varies depending on the type of the resin and the purpose of the treatment, but is usually about 1 to 50 g / m ^{2 in} terms of solid content. The paper having a water-resistant coating formed by the paper processing agent of the present invention is used as a material for various packaging containers, but is not deformed or permeated by water vapor generated from food during heating. Since it can be composted with food, it is particularly suitably used as a material for containers for foods heated by microwave oven such as containers for convenience store lunches. Examples of the present invention will be described below, but the present invention is not limited to these examples. Example 1 Sucrose laurate (Daiichi Kogyo Seiyaku Co., Ltd .; Cosmelike L-160, molecular weight 538) was added to 50 parts of a polylactic acid resin (Shimadzu Corporation; LACTY9030, melting point 150 ° C.). 5 parts and 0.7 part of dioctyl sodium sulfosuccinate solution (Daiichi Kogyo Seiyaku Co., Ltd .; Neocol SW-C, molecular weight 508) were added,
Under stirring with a homodisper, 51 parts of water was added stepwise to form an emulsion, which was then neutralized with 0.35 part of 28% aqueous ammonia to obtain a cloudy liquid emulsion (solid content: 50%, particle size: 0.1%). 7
μm, pH 7.2) 110 parts were obtained. Uncoated neutral high quality paperboard (basis weight 255
g / m ² , thickness 0.31 to 0.32 mm). 10
Was coated with a bar coater of Example 1 and treated in an oven at 150 ° C. for 2 minutes to give a coating amount of 15
After undercoating g / m ^2, the same amount of coating was applied again by the same method, and overcoating and heat treatment were performed. The biodegradability and water vapor resistance of the obtained coated paper were evaluated. For biodegradability, the coated paper was put into a polyester net and buried in the field, and the appearance change was observed. The water vapor resistance is such that steam (approximately 1 kgf / cm ² × 10 minutes, jet diameter 2.5 c
m, a distance of 3 cm from the injection port), and the wettability of the paper was evaluated by visually judging the wet area. Comparative Example 1 A polyethylene film was sandwiched between uncoated neutral high-quality paperboard (basis weight 255 g / m ² , thickness 0.31 to 0.32 mm) and release paper,
The coating was thermocompression-bonded with a hot roll at ℃ (coating amount: 32 g / m ² ). The obtained coated paper was evaluated for biodegradability and water vapor resistance by the methods described above. [Blank] The same paperboard used in the above Examples and Comparative Examples was used, and the biodegradability and the water vapor resistance were evaluated by the above-mentioned method without coating and as the base paper. Table 1 shows the evaluation results of the biodegradability and the water vapor resistance of each of the above samples. [Table 1] According to the paper processing agent of the present invention, a food container which has excellent steam resistance, can withstand heating by a microwave oven or the like, and can be composted with food can be obtained. Further, since the paper processing agent of the present invention is an emulsion, it has the advantages of being versatile and environmentally friendly.

   ────────────────────────────────────────────────── ─── Continuation of front page    F term (reference) 4L055 AG82 AG97 AH37 AJ01 AJ02                       BE08 BE09 EA20 FA19 FA20                       GA05 GA47

Claims (1)

Claims: 1. A paper processing agent comprising a biodegradable resin emulsion and forming a water-resistant coating on paper, wherein the biodegradable resin emulsion is a polyester-based biodegradable material having a melting point of 130 ° C or more. A paper processing agent comprising a resin emulsion obtained by emulsifying a hydrophilic resin with an emulsifier, wherein the carboxylic acid in the resin is neutralized with an alkaline substance.