JPS62182032A - Heat-resistant paper vessel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Sedentary Occupational Use) The present invention relates to a heat-resistant paper container, and more specifically, the present invention relates to a heat-resistant paper container. The present invention relates to a heat-resistant paper container that can be heated or rolled up.

(Prior art) Tray-shaped paper containers are widely used as containers that can be easily filled with food and other contents, but in recent years, with the spread of open containers, microwave ovens, toaster ovens, etc. Uncooked foods are sold in tray-like containers, and when eaten, the containers are placed in the aforementioned heating device.
It is desired to develop a container that can be heated or packed.

As a response to such requests, the special public
No. 890 discloses that after paper stock is prepared at near neutrality, a base paper is made by impregnating it with an aqueous dispersion oil containing an inorganic filler, and then a heat-resistant corrugated film is turbid or pasted on both sides of the base paper. A method of manufacturing paper for food containers is described, which comprises forming the paper and applying a heat-resistant resin to the surface that will become the inside of the container. In addition to aluminum foil, resins such as nitrocellulose lacquer, epoxy, urethane, and fluorine are used for the heat-resistant corrugated film.On the inside of the container, a release agent is applied on top of the heat-resistant film. It is also described that a heat-resistant resin such as a silicone-based resin is applied.

(Problem to be solved by the invention) This container is filled with raw materials such as viro, castella, etc.
Although it can be used for heat treatment at a humidity of about 0 to 250°C, when heating or baking with an open toaster etc., the temperature of the container reaches a high temperature of 300°C or more, and such In terms of heat resistance, it was not yet possible to add enough drops for high-temperature applications.

Paper cellulose fibers begin to carbonize and become colored at a temperature of about 260°C and are completely carbonized at a temperature of about 300°C.

Thus, when a paper container is used in applications where it is heated to a temperature of 300'C or higher, the appearance of the container itself is colored black to the extent that it cannot withstand use, and the strength of the container itself is also significantly lost. It will become.

Therefore, an object of the present invention is to provide a heat-resistant paper container in which the appearance characteristics and the strength of the container wall are maintained at an excellent level even when the container wall is heated to a temperature of 3000° C. or more.

Another object of the present invention is to provide a heat-resistant paper container that can be filled with contents and placed in a heater such as an open toaster for heating or baking.

(Another means to solve the problem) The present inventors selected chemical/4' paper containing a certain amount of inorganic filler as the paper base, and this chemical pulp R [
It has been found that when a heat-resistant coating consisting of a specific polysiloxane coating and an inorganic pigment or inorganic filler dispersed in the coating is provided, excellent appearance characteristics and strength are maintained even after heating. .

That is, according to the present invention, in a tray-shaped heat-resistant paper container consisting of a paper substrate and a heat-resistant wave & layer provided on at least one surface of the paper substrate, the paper substrate has two to six layers on the paper substrate.
Made of chemical pulp paper containing an inorganic filler of 0% by weight, the heat-resistant coating layer has an average number of bonded organic groups per silicon atom of 2.
A heat-resistant paper container is provided, comprising a polysiloxane cured coating having a polysiloxane cured coating, and an inorganic pigment or inorganic filler dispersed in the coating in an amount of 5 to 60 parts by weight per coating.

(Function) In FIG. 1 showing a perspective view of the heat-resistant paper container of the present invention,
This tray-shaped paper container includes a rectangular and flat bottom wall portion 1;
A side wall portion 2a continues to the bottom wall portion 1.

2b, 2c, and 2d, and there are pleats 3 between the side wall portions in contact with VA, and seven rung portions or curl portions 4 are provided on the upper edge of the side wall portion.

2 shows an enlarged cross-sectional structure of the container wall of this paper container. In 1, this container wall 10 consists of a paper substrate 11 and #j thermal coating 12 m, 12b applied to both surfaces of the paper substrate. ing.

In the present invention, first, 2 to 6° weight J[q
A paper substrate consisting of chemical pulp paper containing an inorganic filler 11 of b. This paper substrate was made of sulfide palf (S
By forming it from a chemical valve such as P) or Kraft Pal f (KP), it is possible to suppress carbonization coloring and strength loss at high temperatures to a low level, and also to reduce f of the inorganic filler in the paper substrate. By setting it within the above range, it becomes possible to maintain the strength of the paper at a high level even after high-temperature heating, in combination with the later-described nucleation resistance and percent strength coating.

In the present invention, the surface of the above-mentioned specific paper substrate is coated with a polysiloxane cured coating having an average number of bonded organic groups of less than 2 per silicon atom, and coated with 5 to 60% by weight of an inorganic pigment. A distinctive feature is that a heat-resistant coating consisting of an inorganic filler is provided. In this specification, a cured polysiloxane coating film is defined as a polymer coating film in which silicon atoms, which form the skeleton of coating film molecules, are bonded together in a network via oxygen atoms. This cured polysiloxane coating film has remarkable heat resistance due to the fact that the number of organic groups per silicon atom is suppressed to less than 2 compared to ordinary polyorganosiloxane coating films. Not only that, but also its heat resistance is enhanced by incorporating a relatively large amount of inorganic pigment or inorganic filler, so it has a remarkable thermal protection effect on paper substrates. Furthermore, the polysiloxane cured coating film of the present invention has the effect of tightly adhering the inorganic pigment or inorganic filler contained therein in a relatively large amount to the surface of the paper substrate in a dense state. The strong adhesion is maintained even when the vessel wall is heated to a high temperature of 300°C or higher. Furthermore, this coating film has no tendency to discolor itself at the above-mentioned high temperatures, and has the desirable effect of hiding the carbonized coloration of the paper fibers from the inorganic pigments and inorganic fillers in the coating and the appearance of the container. Do the following.

The above-mentioned effect of the present invention is unexpected from that of conventional heat-resistant papers, which means that with conventional heat-resistant coatings,
At a temperature of 300°C, the coating itself may turn brown or black, crack or peel, and the Hunter whiteness of the surface may be at most 1.
This is clear from the fact that while the 0 coefficient and strength retention rate were at most 10%, in the present invention, a whiteness of 75 mm or more and a strength retention rate of 70 mm or more can be obtained.

(Description of Preferred Embodiments of the Invention) In the present invention, the chemical i4 groups include needle-harvested trees) and hardwoods (sulfite obtained by exposing and treating υ) zf
Lug (BSP), Kraft Nogrug (BKP), etc. are used. Clay, talc, calcium carbonate, titanium dioxide, etc. are used as the inorganic filler, and the amount of inorganic filler in the paper should be in the range of 2 to 60 parts by weight, and in the hakama to be in the range of 4 to 50 parts by weight. . That is, if the thickness is less than the above range, the smoothness, opacity, dimensional stability, etc. required for the container cannot be obtained, and if the thickness is greater than the above range, the absolute strength of the paper tends to decrease. . The basis weight of the paper substrate is generally 100 to 600 jil/m", especially 150 to 400,117
It is desirable that the paper substrate has an elongation of 1.8 inches or more in the vertical and horizontal directions in order to enable press forming into a shape such as a tray. For this purpose, it is desirable that at least 10% by weight, particularly at least 20% by weight, of the chemical pulp described above be composed of softwood selvedge (NBKP or NBSP).

The polysiloxane cured coating that forms the entire heat-resistant coating has an average number of organic groups per silicon atom in the final state of less than 2, especially from 1 to 0. It can be obtained by condensation curing of organic silicate and/or organosiloxane monomers or oligomers within the range of the value of l.

One typical example is a cured coating in which the number of organic groups per silicon atom is zero; this type of cured coating is
It can be obtained by curing a heptamer or oligomer organic silicate such as ethyl silicate (81(QC2H5)), isopropyl silicate, butyl silicate or the like through hydrolysis and condensation.

Although this type of cured coating film has some disadvantages in workability, it is outstandingly excellent in coating film density and heat resistance.

Other typical examples include organosiloxanes containing three or more alkoxy groups in the molecule, for example, where R is an alkyl group, R1 is a methyl group, ethyl group, or 2-enyl group, and R2 is a methyl group, ethyl group, phenyl group, alkoxy group or hydrogen atom, at least one R2 in the molecule is an alkoxy group, and n
It is a positive integer greater than or equal to l″t2.

The organosiloxane monomers or oligomers are condensed by hydrolysis of the alkoxy group.

Although this type of cured coating film has slightly inferior heat resistance compared to Maedagi, it has excellent workability.

The condensation of these silicate esters and alkoxy group-containing organosiloxanes proceeds in the presence of moisture without any catalyst.
Condensation curing is preferably carried out in the presence of a silanol condensation catalyst such as oleate or tetrabutyl titanate. It is desirable to use the condensation catalyst in an amount of 0.1 to 5 weight percent of the solid lunch box.

The silicate ester or alkoxy group-containing organosiloxane contains an inorganic pigment and/or an inorganic filler. Inorganic pigments and inorganic fillers include titanium dioxide, iron oxide, mica, magnesia, alumina, aluminum hydroxide, magnesium carbonate, magnesium hydroxide,
Examples include calcium silicate, magnesium silicate, jAM type magnesium silicate (including Merck), calcium carbonate, clay, fired clay, etc., but are not limited to the examples.

These inorganic pigments and/or inorganic fillers are preferably contained in an amount of 5 to 60% by weight, particularly 30 to 50% by weight. If the amount is less than the above range, the improvement in heat resistance and the hiding effect of the paper substrate will be insufficient, while if the amount is more than the above range, the adhesion and denseness of the coating will tend to be lost.

The thickness of the heat-resistant coating applied to the surface of the paper substrate is generally in the range of 1 to 30 μm, particularly 5 to 10 μm, and if it is thinner than the above range, the heat resistance and hiding effect will be If the thickness is insufficient, or if it is thicker than the above range, it will lose its properties as a container and will be disadvantageous in terms of cost.

From the viewpoint of productivity, it is desirable to form a heat-resistant coating on a paper substrate and then form it into the shape of a container such as a tray, but it is of course possible to form the paper substrate into a container shape and then apply the heat-resistant coating to this molded product. It is also possible to do so.

Alternatively, a heat-resistant coating may be applied to a paper substrate, the coating may be formed into a container in an uncured or semi-cured state, and the coating may be finally cured in this form.

(Example) The invention is illustrated by the following example.

Example 1 The basis weight was 35017 m'', 30 wt% softwood pulp (NBKP) was used as chemical pulp, and hardwood pulp f (LB
KP) 70wt% and 5% talc as an inorganic filler.
A paint consisting of 10 wt % Et-n-white as resin components, 25 wt % mica powder, and 5 wt 4 solvent was applied to both sides of the paper substrate containing w with a percoater.
Dry cured in the open at 80°C for 6 minutes.

The amount of paint applied was 20117 m'' on one side.

Using paper coated with the thus obtained polysiloxane paint on both sides, it was press-molded into a shape of 186 nm long and 10 mm wide.
A rectangular tray with crR1 depth of 2 m was molded. Place 3 skewers of salty yakitori that you have stored in the refrigerator in this square tray.
Heat it in an open toaster for 4 minutes. After heating, I took out the yakitori from the opener, and when I tasted the yakitori, it was at the right temperature and delicious. At this time, the surface of the square tray will not burn,
No discoloration was observed. Furthermore, the surface temperature of the square tray during heating was measured and found to be 300°C.

Example 2 In Example 1, before applying the polysiloxane paint, an epoxyphenol paint was applied as a pace coat using a bar coater and dried and cured at 180°C for 6 minutes. The amount of pace coat applied was 1017 m''.

Using the thus obtained paper coated with two layers of epoxyphenol-based pace coat and polysiloxane-based top coat, it was press-molded to a size of 18 crn in length and 10 crn in width.
cIn, a rectangular tray with a depth of 2α was molded. Three skewers of Jigarasu with sauce were placed in this square tray and stored in the refrigerator for 2 days. When the tray was removed from the refrigerator after being stored for 2 days, the yakitori sauce had not penetrated into the tray at all, and no deformation of the paper tray was observed. The tray containing the yakitori with sauce was heated for 4 minutes in an open toaster. After heating, I took out the yakitori from the opener, and when I tasted the yakitori, it was at the right temperature and delicious. At this time, the surface of the square tray was not burnt and no discoloration was observed.

In addition, when the surface temperature of the square tray during heating was measured, 3
It was 00℃.

Comparative Example 1 In Example 1, a square tray made of paper without any polysiloxane paint was molded and the same test was conducted, and the surface of the square tray turned brown after heating. In addition, a decrease in paper strength was observed, and the wall surface of the square tray easily broke when force was applied by hand.

Example 3 Using the paper used in Example 1, a rectangular tray with a length of 18 crR%, a width of 10 crn, and a depth of 2α was formed by press molding. Sil (0(CH,) 2 ) containing titanium white was spray coated on both sides of this square tray.
A solution of CH) 4 in Inglovil alcohol was coated and dried in an oven at 180° C. for 10 minutes. The thickness of the coating film was 10 μm. Macaroni gratin was placed in this square tray and heated in a gas oven over medium heat for 10 minutes. After heating, the tray was removed from the oven and the macaroni gratin was tasted.The center of the macaroni gratin had been thoroughly heated and was delicious. Also at this time,
No discoloration was observed on the surface of the square tray.

On the other hand, when the same square tray containing macaroni gratin was placed in a microwave oven and heated, the heating finished in 5 minutes.

In this way, this square container has good microwave penetration,
It was possible to heat efficiently in a microwave oven.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the heat-resistant paper container of the present invention, and FIG. 2 is a cross-sectional structural diagram of the container wall of the paper container of the present invention. , 2b, 2e and 2d are side wall parts, 3 is a fold part, 4 is a flange part or curl part, 10
11 is the paper substrate, 12a is the vessel wall. 12b indicates a heat-resistant coating layer.

Claims (1)

[Claims] (1) In a tray-shaped heat-resistant paper container comprising a paper substrate and a heat-resistant coating layer provided on at least one surface of the paper substrate, the paper substrate contains 2 to 60% by weight of an inorganic filler per paper substrate. A chemical pulp paper, the heat-resistant coating layer comprising a polysiloxane cured coating having an average number of bonded organic groups per silicon atom of less than 2 and 5 to 60 per coating dispersed in the coating.
A heat-resistant paper container characterized by comprising an inorganic pigment or an inorganic filler in an amount by weight of an inorganic pigment or an inorganic filler.