JP6850177B2 - Raw material sheet and foamable paper container - Google Patents

Description

The present invention relates to a raw material sheet and a foamable paper container.

Generally, a foamable paper sheet and a foamable paper container are made by laminating low-density polyethylene on one side of a base paper and high-density or medium-density polyethylene on the other side, and heating the base paper in an oven. The surface of the low-density polyethylene has a print layer including a print pattern such as a decorative pattern, a trade name, a company name, and a barcode.

It has been conventionally known that an ink for forming a printing layer contains a polyamide resin or the like and a cellulose derivative as a binder component. The ink remarkably suppresses the foaming of low-density polyethylene, and after foaming in the printed portion and the non-printed portion of the printed layer, or in the printed portion and the overprinted portion in which printing is further performed on the printed portion. There is a difference in the thickness of low density polyethylene. As a result, there is a problem that the printed portion or the overcoated portion becomes a concave portion, a step is generated, and the printing becomes unclear.

As an ink for improving the unevenness of the surface of the printed layer, Patent Document 1 contains a colorant, a binder resin and a solvent, and the binder resin contains a urethane resin and a vinyl chloride / vinyl acetate copolymer. Based on the total weight of the urethane resin and the vinyl chloride / vinyl acetate copolymer, the mixing ratio of the urethane resin: vinyl chloride / vinyl acetate copolymer is 50:50 to 99: 1, and the elongation rate of the binder resin is 50:50 to 99: 1. An ink having a value of 400% to 3,000% is disclosed.

Japanese Patent No. 4619455

The ink disclosed in Patent Document 1 contains chloride, and a better ink is required in terms of safety and environment.

Therefore, the present invention has been made in view of the above circumstances, and is a raw material sheet and a raw material sheet for which an foamable paper product containing an ink having a small impact on the environment and having a smooth print layer surface and an excellent appearance can be obtained. Provided is an effervescent paper container using.

As a result of diligent research to solve the above problems, the present inventors have made ink substantially free of chloride by using nitrocellulose instead of chloride as necessary for the ingredients of the ink. It was found that a foamable paper product having good foamability could be obtained by using the above, and the present invention was completed.

That is, the present invention includes the following aspects.
[1] A raw material sheet used for a foamable paper product, which is made of a paper base material provided with a foam layer obtained by heating a thermoplastic resin layer having at least one layer or more of an ink-coated portion on one side, and the ink is colored. A raw material sheet containing an agent and a binder resin and substantially free of chloride, wherein the binder resin contains a urethane-based resin, or a urethane-based resin and nitrified cotton.
[2] The raw material sheet according to [1], wherein the glass transition point of the urethane resin is −20 ° C. or higher and 30 ° C. or lower.
[3] The raw material sheet according to [1] or [2], wherein the urethane-based resin is a polyether urethane resin.
[4] The raw material sheet according to any one of [1] to [3], wherein the content of the urethane-based resin in the resin solid content of the binder resin is 50% or more.
[5] The raw material sheet according to any one of [1] to [4], wherein the binder resin further contains silicon dioxide.
[6] A foamable paper container comprising the raw material sheet according to any one of [1] to [5].

According to the present invention, there is provided a raw material sheet and a foamable paper container using the raw material sheet, which contains an ink having a small impact on the environment and can obtain a foamable paper product having a smooth print layer surface and excellent appearance. can do.

It is sectional drawing which shows typically one Embodiment of the raw material sheet (before foaming) of this invention. It is sectional drawing which shows typically one Embodiment of the raw material sheet (after foaming) of this invention.

Hereinafter, a mode for carrying out the present invention (hereinafter, may be simply referred to as “the present embodiment”) will be described in detail. The present embodiment shown below is an example for explaining the present invention, and is not intended to limit the present invention to the following contents. The present invention can be appropriately modified and implemented within the scope of the gist thereof.

≪Raw material sheet≫
In one embodiment, the present invention is a raw material sheet used for a foamable paper product, from a paper base material provided with a foam layer formed by heating a thermoplastic resin layer having at least one or more ink-coated portions on one side. Provided is a raw material sheet in which the ink contains a colorant and a binder resin and substantially contains no chloride, and the binder resin contains a urethane-based resin or a urethane-based resin and nitrified cotton.

According to the raw material sheet of the present embodiment, a foamable paper product having a smooth printed layer surface and an excellent appearance can be obtained. Further, since the ink-coated portion provided in the raw material sheet of the present embodiment does not substantially contain chloride, it has a small environmental load and is more suitable for use in food applications.

In addition, in this specification, "substantially free of chloride" means a state which does not contain chloride at all, or contains only a trace amount of chloride which does not affect the environment.

<Structure>
1A and 1B are cross-sectional views schematically showing an embodiment of the raw material sheet of the present invention. FIG. 1A shows a raw material sheet before heating and foaming, and FIG. 1B shows a raw material sheet after heating and foaming.
The raw material sheet 10 before foaming of the present embodiment has an ink non-coated region A and an ink coated region B arranged adjacent to each other in a plan view, and has a non-foamed thermoplastic resin layer 2a and a paper base material 3. , The foamed thermoplastic resin layer 2b, and the printing layer 1 (first ink coating portion 1a and second ink coating portion 1b) are laminated in this order.
Further, in the foamed raw material sheet 20 of the present embodiment, the foamed layer 2b'heats the foamed thermoplastic resin 2b having the printing layer 1 (the first ink-coated portion 1a and the second ink-coated portion 1b). It is composed of a normal foamed portion 4 existing in the ink non-painted region A and a printed foamed portion 5 existing in the ink coated region B. By coating with ink, the printed foamed portion 5 is slightly suppressed from foaming as compared with the normal foamed portion 4. Further, the print foaming portion 5 includes a first print foaming portion 5a formed in a region where the first ink coating portion is exposed on the surface, that is, a one-layer ink coating portion, and a second ink coating portion. Consists of a region exposed on the surface, that is, a second printed foam portion 5b formed in the two layers of ink-coated portions.

In the foamed raw material sheet 20 of the present embodiment, the foaming thickness in the non-ink-coated portion (normally foamed portion 4) is X, and the foaming thickness in the one-layer ink-coated portion (first printed foamed portion 5a) is Y. The foaming suppression rate represented by the following formula (1) is 54% or less, preferably 53% or less, and more preferably 52% or less.
Foam suppression rate (%) = (1-Y / X) x 100 (1)
When the foaming suppression rate is within the above range, the boundary between the non-ink-coated area and the ink-coated area becomes a smooth printed matter, and the printed matter can be clearly seen.

For X and Y, the average value of the measured values of the foam thickness in the non-ink-coated portion (normally foamed portion 4) or the one-layer ink-coated portion (first printed foamed portion 5a) may be used.
Further, in FIGS. 1A and 1B, a raw material sheet having a two-layer ink coating portion is illustrated, but the foam thickness in the ink coating portion of two or more layers, for example, three layers and four layers, is also the ink coating of each layer. The foam thickness in the portion may be measured, and the average value thereof may be used to apply a numerical value to the above formula (1) to calculate the foam suppression rate.
For example, in FIG. 1B, when the foam thickness in the two-layer ink-coated portion is Z, the foam suppression rate may be calculated by using Z instead of Y in the above formula (1). That is, the foaming suppression rate in the second printed foamed portion 5b with respect to the normal foamed portion 4 is represented by the following formula (2).
Foaming suppression rate (%) = (1-Z / X) x 100 (2)

Further, the colors of the inks used in the first ink coating portion and the second ink coating portion may be the same color or different colors.

Further, in the foamed raw material sheet 20 of the present embodiment, the foam thickness in the ink-coated portion (first printed foamed portion) of the first layer is Y, and the foam thickness of the two-layer ink coated portion (second printed foamed portion) is set to Y. When the foam thickness is Z, the foam suppression rate represented by the following formula (3) is 54% or less, preferably 53% or less, and more preferably 52% or less.
Foam suppression rate (%) = (1-Z / Y) x 100 (3)
When the foaming suppression rate is within the above range, the surface of the print layer is smooth and the print can be clearly seen.

The raw material sheet of the present invention is not limited to those shown in FIGS. 1A to 1B, and a part of the raw material sheets shown in FIGS. 1A to 1B has been changed or deleted within a range that does not impair the effects of the present invention. Or, other configurations may be added to those described so far.

For example, the raw material sheets shown in FIGS. 1A to 1B may include two or more layers, for example, three layers and four layers of ink-coated portions. Above all, the ink coating portion is preferably 2 layers or more and 8 layers or less.

Further, the raw material sheets shown in FIGS. 1A to 1B may be those in which ink is coated on the entire surface and covered with a printing layer, that is, those not provided with an ink-uncoated portion.

Further, the raw material sheets shown in FIGS. 1A to 1B may be provided with foamed thermoplastic resin layers on both sides.

<Constituent material>
The materials constituting the raw material sheet of the present embodiment will be described below.

[Print layer]
In the raw material sheet of the present embodiment, the thickness of the ink-coated portion before heating after drying is preferably 2 μm or less per layer. When it is 2 μm or less, foaming is not suppressed and a smooth printed surface can be obtained.
When the ink-coated portion is, for example, two layers, the printed layer after drying is preferably 4 μm or less. For example, when the ink-coated portion is, for example, three layers, the printed layer after drying is 6 μm or less. Is preferable.

(ink)
The ink used for the printing layer of the present embodiment is obtained by adding a solvent to the structure of the ink-coated portion in a dry state. That is, the ink contains a colorant, a binder resin, and a solvent.
Further, since the ink used for the printing layer of the present embodiment does not substantially contain chloride, the environmental load is small.

◎ Colorant The colorant may be an inorganic colorant or an organic colorant as long as it does not substantially contain chloride.
Examples of the inorganic colorant include titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, aluminum hydroxide, talc, clay, kaolin, chromium oxide, silica, carbon black, aluminum, mica (mica) and the like. Can be mentioned.
Titanium oxide is preferable as the white colorant, and titanium oxide having a basic pigment surface is more preferable, from the viewpoints of coloring power, hiding power, chemical resistance, and weather resistance. Although aluminum is in the form of powder or paste, it is preferably used in the form of paste from the viewpoint of handleability and safety, and whether to use leafing or non-leafing is appropriately selected from the viewpoint of brightness and concentration.
Barium sulphate, calcium carbonate, aluminum hydroxide, talc, clay and kaolin are called extender pigments and are used as bulking agents to improve fluidity, strength and optical properties.
On the other hand, examples of the organic colorant include organic pigments and dyes used in general inks, paints, recording agents and the like. For example, azo type, phthalocyanine type, anthraquinone type, perylene type, perinone type, quinacridone type, thioindigo type, dioxazine type, isoindolinone type, quinophthalone type, azomethine azo type, dictopyrrolopyrrole type, isoindoline type and the like can be mentioned.
However, as the colorant, those such as phthalocyanine green containing chloride are excluded.
The content of these colorants can be appropriately selected in consideration of the desired color tone of the ink, etc., but generally, it may be 50% by weight or less based on the total weight of the ink, and is the upper limit value. By the following, the content of the colorant is such that the required inking concentration can be obtained.

When the ink used for the printing layer of the present embodiment is white, the content of the white pigment may be generally 20% by weight or more and 50% by weight or less based on the total weight of the ink, and is within the above range. Therefore, the content of the pigment is such that the required inking concentration can be obtained. From the viewpoint of hiding property, pigment concentration, and light resistance, the white pigment is preferably titanium dioxide.
When the ink used in the present embodiment is colored, examples of the colored pigments contained include colored organic pigments and colored inorganic pigments such as red iron oxide, prussian blue, ultramarine, carbon black, and graphite. .. From the viewpoint of color development and light resistance, the colored pigment is preferably an organic pigment. Generally, the content of the colored pigment may be 10% by weight or more and 30% by weight or less based on the total weight of the ink, and if it is within the above range, the content of the pigment that can obtain the required deposition concentration It becomes the quantity.

◎ Binder resin The binder resin includes urethane-based resin, urethane-based resin, and nitrified cotton.
When the ink used for the printing layer of the present embodiment is white, the dispersibility of the pigment is excellent, so that the ink need only contain a urethane resin as the binder resin. On the other hand, when the ink used in the present embodiment is colored, the ink preferably contains nitrocellulose as the binder resin in addition to the urethane-based resin in order to improve the dispersibility of the pigment.

◯ Urethane-based resin The urethane-based resin has a glass transition point of −20 ° C. or higher and 30 ° C. or lower, preferably −15 ° C. or higher and 0 ° C. or lower. When the glass transition point of the urethane resin is at least the above lower limit value, the occurrence of blocking can be suppressed, and when it is at least the above upper limit value, the suppression of foaming can be suppressed.
In general, "blocking" means that the surface of the raw material sheet having the printing layer and the surface on the opposite side of the raw material sheet stick to each other when printing, drying, and subsequently winding the ink.

Further, in the present specification, the "urethane-based resin" means a urethane resin in a broad sense including a general urethane resin conventionally used in the art or a modified urethane resin such as a urethane urea resin. The urethane-based resin used as the binder resin in the present embodiment is not particularly limited depending on the production method thereof, and is various urethane-based resins obtained by applying a known or well-known method for urethane-based resins. All you need is. Specific examples thereof include a urethane resin such as a polyether urethane resin (the above-mentioned "general urethane resin"), a polyurethane urea resin, and the like. Above all, as the urethane-based resin used as the binder resin in the present embodiment, a polyether urethane resin is preferable.

-Urethane resin The urethane resin can be produced by reacting a polyol compound with an organic diisocyanate.

1. 1. Polyurethane compound Examples of the polyol compound used in the production of the urethane resin include various known polyols as shown below.
(1) Polymers such as ethylene oxide, propylene oxide and tetrahydrofuran, or polyether polyols such as copolymers;
(2) Others Polycarbonate diols, polybutadiene glycols, bisphenol A glycols obtained by adding ethylene oxide or propylene oxide;
(3) Dimer diols.
These various polyols may be used alone or in combination of two or more.

The number average molecular weight of the polyol is appropriately determined in consideration of properties such as solubility, drying property, and blocking resistance of the urethane resin obtained as a reaction product. For example, usually, the range of 500 or more and 10,000 or less is preferable, and the range of 500 or more and 6,000 or less is more preferable. When the number average molecular weight is at least the above lower limit value, it is possible to prevent the solubility from being lowered and the printability from being lowered. Further, when the number average molecular weight is not more than the above upper limit value, it is possible to prevent the drying property and the blocking resistance from being lowered.

2. Organic Diisocyanate The organic diisocyanate used in the production of the urethane resin may be various known diisocyanates of aromatic, aliphatic, or alicyclic group. Specifically, for example, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzylisocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate. , 1,3-phenylenediocyanate, 1,4-phenylenediocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, cyclohexane -1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis (isocyanatemethyl) cyclohexane, methylcyclohexane diisocyanate, norbornan diisocyanate, m-tetramethylxyl Examples thereof include range isocyanate and dimerized isocyanate obtained by converting the carboxyl group of dimer acid into an isocyanate group.

3. 3. Manufacturing Method The manufacturing method of the urethane resin may be a conventionally known or well-known method, and is not particularly limited. For example, when the polyol compound is reacted with the organic diisocyanate, other conditions are not limited except that the organic diisocyanate is excessively used with respect to the polyol compound. In the method for synthesizing urethane resin, it is preferable that the molar equivalent ratio of isocyanate group / hydroxyl group is in the range of 1.2 / 1-3 / 1. When the molar equivalent ratio of isocyanate group / hydroxyl group is at least the above lower limit value, it is possible to prevent the obtained urethane resin from becoming fragile. On the other hand, when the molar equivalent ratio of isocyanate group / hydroxyl group is not more than the above upper limit value, it is possible to suppress an increase in viscosity during production of the urethane resin and prevent gelation during the reaction.
The temperature of the polyurethane-forming reaction during the production of urethane resin is usually in the range of 80 ° C. or higher and 200 ° C. or lower, and preferably in the range of 90 ° C. or higher and 150 ° C. or lower.

The polyurethane-forming reaction may be carried out in a solvent or in a solvent-free atmosphere. When a solvent is used, the same solvent as that exemplified in "◎ Solvent" described later can be appropriately selected from the viewpoint of controlling the reaction temperature, viscosity and side reaction.
Further, when the polyurethane-forming reaction is carried out in a solvent-free atmosphere, it is preferable to raise the temperature to such an extent that sufficient stirring can be performed to lower the viscosity in order to obtain a uniform urethane resin. The reaction time of the polyurethane-forming reaction is preferably 10 minutes or more and 5 hours or less. The end point of the reaction can be determined by methods such as viscosity measurement, confirmation of NCO peak by IR measurement, and NCO% measurement by titration.

-Polyurethane urea resin The polyurethane urea resin is obtained by reacting the above-mentioned polyol compound with the above-mentioned organic diisocyanate to synthesize a urethane resin having an isocyanate group at the terminal, and then adding an amine compound or an amide compound as a chain extender and a reaction terminator. It is a resin obtained by introducing a urea bond into the urethane resin.

1. 1. Chain extender Examples of the chain extender that can be used to introduce a urea bond include various known amines. For example, ethylenediamine, propylenediamine, hexamethylenediamine, triethylenetetramine, diethylenetriamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine. , Di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine and other diamines having a hydroxyl group in the molecule, and dimer diamine obtained by converting the carboxyl group of dimer acid into an amino group. Be done. These may be used alone or in combination of two or more.

2. Reaction terminator Examples of the reaction terminator include an aliphatic amine compound having a long-chain alkyl group of C8 or more and C22 or less, a fatty acid amide compound, and the like.
Examples of the aliphatic amine compound include octylamine, laurylamine, coconutamine, myristylamine, stearylamine, oleylamine, palmitylamine, dibutylamine and the like. These may be used alone or in combination of two or more.
Examples of the fatty acid amide compound include octanoic acid amide, decanoic acid amide, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, bechenic acid amide, oleic acid amide, erucic acid amide, linoleic acid amide and linolene. Acid amide and the like can be mentioned. These may be used alone or in combination of two or more.

3. 3. Manufacturing method The manufacturing method of the urethane resin is as described above. Further, the production method for introducing a urea bond into the urethane resin is not particularly limited.
For example, when the number of free isocyanate groups existing at both ends of the urethane resin is 1, the total number of amino groups in the chain extender and reaction terminator used is within the range of 0.5 or more and 1.3 or less. It is preferable to do so. When the total number of the amino groups is at least the above lower limit value, the effect of improving the drying property, blocking resistance, and coating film strength can be sufficiently obtained. On the other hand, when the total number of the amino groups is not more than the above upper limit value, it is possible to prevent the chain extender and the reaction terminator from remaining unreacted and the odor from remaining on the printed layer.

The urethane resin is preferably contained in an amount of 50% or more, more preferably 60% or more, further preferably 70% or more, and preferably 80% or more of the resin solid content of the binder resin. It is particularly preferable, and it is most preferable to contain 90% or more.
When the content of the urethane-based resin in the binder resin is within the above range, foaming of the thermoplastic resin is hardly suppressed, and a raw material sheet having a smooth printed surface can be obtained.

○ Vitrified cotton The nitrified cotton is usually called nitrocellulose, and can be obtained by a known method such as a method in which purified natural cellulose is esterified with a mixed acid and the hydroxyl group in the cellulose is replaced with a nitric acid group.
In general, nitrocellulose has high coating film strength, elastic modulus, and surface hardness, so that it can be used for various purposes, and the solubility can be selected by the nitrogen content and the solution viscosity can be selected by the degree of polymerization.
In the present specification, the "nitrogen content" means the weight% of nitrogen atoms in the resin, and the larger the amount of substitution of the hydroxyl group of cellulose with a nitric acid group, the larger the value. In the case of industrial nitricized cotton, the nitrogen content is generally 10.7 or more and 12.2 or less. The nitricized cotton used in the present embodiment may be L cotton having a nitrogen content of 10.7 or more and 11.5 or less, or a low nitrogen content type called L type, and has a nitrogen content of 11.5 or more. It may be H cotton having a content of 12.2 or less or a high nitrogen content type called H type, and there is no particular limitation.
Further, the average degree of polymerization of the nitricized cotton used in the present embodiment may be, for example, 30 or more and 150 or less. When the average degree of polymerization of nitricized cotton is at least the above lower limit value, the toughness of the film can be ensured, and the ink has excellent alcohol bleeding resistance and blocking resistance. On the other hand, when the average degree of polymerization of the nitrocellulose resin is not more than the above upper limit value, it is possible to prevent the viscosity of the nitrocellulose solution or the ink from increasing.

When the ink is colored, the resin solid content of the binder resin preferably contains 50% or less of nitrocellulose, more preferably 10% or more and 40% or less, and 20% or more and 30% or less. More preferred.
When the content of nitricized cotton in the binder resin is within the above range, the dispersibility of the pigment can be improved and the foaming suppression rate can be reduced. Further, it is possible to prevent the ink surface from cracking in the ink-coated portion of the raw material sheet after foaming.

○ Content of binder resin In the present embodiment, the content of the binder resin is preferably 15% by mass or more and 25% by weight or less based on the total mass of the ink. When the content of the binder resin is at least the above lower limit value, an appropriate ink viscosity can be obtained, and when it is at least the above upper limit value, it is possible to prevent the ink fluidity from being lowered, and during ink production and printing. Work efficiency can be improved.

(8) Solvent The solvent contained in the ink used for the printing layer of the present embodiment may be any known compound that can be usually used as a solvent for printing ink. For example, alcohol solvents such as methanol, ethanol, isopropanol, n-propanol, n-butanol; ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone; ester organic solvents such as methyl acetate, ethyl acetate, propyl acetate and butyl acetate. Solvents; aliphatic hydrocarbon-based organic solvents such as n-hexane, n-heptane, n-octane; alicyclic hydrocarbon-based organic solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, cycloheptane, cyclooctane and the like. .. Considering the solubility and drying property of the binder resin, it is preferable to mix and use the above-mentioned various solvents.
In the present embodiment, the solvent content may be, for example, 30% by mass or more based on the total mass of the ink.

◎ Constituent pigment The ink used for the printing layer of the present embodiment preferably further contains an extender pigment. By containing the extender pigment, an ink having better foamability can be obtained.

Examples of the extender pigment include silicon dioxide, talc, kaolin, magnesium oxide and the like. Above all, silicon dioxide is preferable as the extender pigment contained in the ink in the present embodiment.
The silicon dioxide may be, for example, a compound known as "synthetic silica" produced by a known method. Typical production methods for synthetic silica are a wet method that produces ultrafine powder-containing silicic acid by reacting sodium silicate made from high-purity silica sand with an acid, or a wet method that burns and hydrolyzes silicon tetrachloride in the gas phase. There is a dry method.

The silicon dioxide used in the present embodiment is not particularly limited by the synthetic method, and examples thereof include untreated silicon dioxide (untreated silica).
The particle size of silicon dioxide used in the present embodiment is preferably 2 μm or more and 20 μm or less, and more preferably 3 μm or more and 10 μm or less. By using silicon dioxide having a particle size of not more than the above lower limit value, it is possible to prevent the viscosity of the ink from increasing and prevent the ink state from deteriorating. Further, by using silicon dioxide having a particle size equal to or less than the above upper limit value, it is possible to prevent the ink film from being inferior in foaming followability to the foaming of the low melting point resin film used as the foaming thermoplastic resin during the heat treatment during container manufacturing. be able to.

The particle size of silicon dioxide is generally measured by a Coulter counter method using a change in electrical resistance, a laser method using light scattering, or the like. In the present embodiment, it means the average particle size obtained by the measurement using the laser method.

When silicon dioxide is contained in the present embodiment, the content of silicon dioxide is preferably 0.2% by mass or more and 5% by mass or less, and 0.5% by mass or more and 3.5% by mass or more, based on the total mass of the ink. It is more preferably mass% or less. When the content of silicon dioxide is in the above range, an ink having better foamability can be obtained.

◎ Other components In addition, the ink used for the printing layer of the present embodiment is an auxiliary agent (for example, a polyolefin wax such as polyethylene wax; fatty acid amide, fatty acid ester, paraffin wax, polytetrafluoroethylene (PTFE) wax. , Various known waxes such as carnauba wax), various ink additives such as defoaming agent, leveling agent, pigment dispersant, and plasticizing agent may be contained.

[Foam thermoplastic resin layer]
In the raw material sheet of the present embodiment, the foamed layer is formed by heating a thermoplastic resin layer. That is, the foamed layer is a foamed thermoplastic resin layer (foamed thermoplastic resin layer). The thermoplastic resin used for the foamed thermoplastic resin layer is not particularly limited as long as it can be extruded and laminated and can be foamed, and either a crystalline resin or a non-crystalline resin can be used. .. Examples of the crystalline resin include polyolefin resins such as polyethylene, polypropylene and polymethylpentene; polyester resins, polyamides, polyacetals, PPS resins and the like. Examples of the non-crystalline resin include polystyrene, polyvinyl chloride, ABS resin, acrylic resin, modified PPE, polycarbonate, polyurethane, polyvinyl acetate, and non-crystalline polyethylene terephthalate (PET). The melting point of these thermoplastic resins is preferably about 80 ° C. or higher and 120 ° C. or lower. Further, these thermoplastic resins may use a single resin in a single layer or a plurality of resins in a plurality of layers, but are preferably a single layer from the viewpoint of foamability.

Among them, polyethylene is preferable as the thermoplastic resin used for the foamed thermoplastic resin layer because it is excellent in laminating suitability and foamability. Polyethylene is broadly classified into linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, and high-density polyethylene.
The density, linear low density polyethylene 888kg / ^{m 3} or more 910 kg / ^{m 3} or less, low density polyethylene 910 kg / ^{m 3} or more 925 kg / ^{m 3} or less, medium-density polyethylene 925 kg / ^{m 3} or more 940 kg / ^{m 3} Hereinafter, the high-density polyethylene is 940 kg / m ³ or more and 970 kg / m ³ or less.
The melting point of linear low-density polyethylene is 55 ° C or higher and 120 ° C or lower, low-density polyethylene is 105 ° C or higher and 120 ° C or lower, medium-density polyethylene is 120 ° C or higher and 125 ° C or lower, and high-density polyethylene is 125 ° C or higher and 135 ° C or lower. It is as follows.

The thickness of the foamed layer (foamed thermoplastic resin layer) is not particularly limited as long as it is sufficient to impart at least one of the desired heat insulating properties and design properties, and is not particularly limited. , The first print foaming portion and the second print foaming portion may be 0.01 mm or more and 4 mm or less, and the foam suppression portion may be 0 mm or more and 1 mm or less.

[Non-foamed thermoplastic resin layer]
In the raw material sheet of the present embodiment, in order to improve the foaming efficiency, the opposite wall surface side of the wall surface having the foamed thermoplastic resin layer of the body member is made of a thermoplastic resin having a melting point higher than that of the foamed thermoplastic resin layer and is heat-treated. It is preferable to cover it with a thermoplastic resin layer (non-foamed thermoplastic resin layer) that does not foam when it is formed, or an aluminum foil or the like. If one side of the paper base material is left as it is (the state where it is not coated with the laminate or coating layer), the moisture in the paper will evaporate into the atmosphere from this uncoated surface during the heat treatment, which is sufficiently reliable. It becomes difficult to foam. Therefore, by providing such a coating layer, the moisture in the paper can be efficiently contributed to foaming. When the raw material sheet is used as a foamable paper container, if these non-foamed thermoplastic resin layers, aluminum foil, etc. are present on the inner wall surface side of the body member, the filling liquid or the like permeates into the paper. Can be prevented, which is preferable.

The thermoplastic resin used for the non-foamed thermoplastic resin layer of the raw material sheet of the present embodiment may be the same as or different from the foamed thermoplastic resin layer. If they are the same, the melting points can be different by making the densities different. For example, when polyethylene is selected as both thermoplastic resins, the foamed thermoplastic resin layer is low-density polyethylene, and the non-foamed thermoplastic resin layer is medium-density or high-density polyethylene. The difference in melting point between the foamed thermoplastic resin layer and the non-foamed thermoplastic resin layer in the thermoplastic resin is preferably 5 ° C. or more, and the melting point of the thermoplastic resin in the non-foamed thermoplastic resin layer is melted during heating. It is not particularly limited as long as it can prevent the diffusion of evaporated water, but it is preferably 125 ° C. or higher.

[Paper base material]
As the paper base material used for the raw material sheet of the present embodiment, for example, chemical pulp and mechanical pulp obtained from wood are mainly used, and non-wood pulp such as kenaf and bamboo is blended therein as needed. Examples thereof include, and are not limited to, a paper substrate obtained by making a paper by the paper making process of. Above all, the paper base material used for the raw material sheet of the present embodiment preferably contains chemical pulp. Since it contains chemical pulp, it is easier to increase the density than when mechanical pulp is used, and it suppresses yellowing when exposed to light for a long time or stored at high temperature for a long time. In addition, the strength and rigidity when it is assumed to be used for a container are increased.

The blending ratio of the chemical pulp with respect to the total raw material pulp used for the paper base material is preferably 80% by weight or more, more preferably 90% by weight or more, still more preferably 95% by weight or more.
Further, it is preferable that the chemical pulp contains a large amount of fibers derived from coniferous trees because it has high foamability.
The blending ratio of the softwood-derived chemical pulp with respect to the total raw material pulp used for the paper base material is preferably 5% or more, more preferably 10% or more, still more preferably 20% or more.

The base paper basis weight of the paper base material may be, for example, 25 g / m ² or more and 500 g / m ² or less. When the raw material sheet of the present embodiment is used for a container, the base paper basis weight of the paper base material may be, for example, 30 g / m ² or more and 400 g / m ² or less in consideration of foamability.
When the base paper basis weight of the raw material sheet of the present embodiment is at least the above lower limit value, it is possible to sufficiently secure the amount of water required for imparting heat insulating properties and designability by foaming. Further, when the base paper basis weight of the raw material sheet of the present embodiment is not more than the above upper limit value, it is easy to process after foaming, and the cost of the paper base material can be suppressed within an appropriate range.

The drainage degree (“Canadian Standard” freshens; CSF) of the pulp used for the paper substrate is preferably 150 mL or more and 600 mL or less, and more preferably 200 mL or more and 580 mL or less. When the CSF of the pulp is 600 mL or less, it is difficult for water vapor to permeate inside the paper base material, and it is difficult for water vapor to escape from the end face of the paper base material, so that the foam thickness becomes large. When the CSF of the pulp is 200 mL or more, the power consumption for beating the pulp and lowering the degree of drainage is not increased, which is excellent in terms of cost. In addition, it is possible to relax the equipment support for enhancing the pulp beating capacity.

The density of the paper substrate ^{is preferably 0.6 g / cm 3} or more, more preferably 0.7 g / cm ³ or more, and even more preferably 0.8 g / cm ³ or more.
The thickness of the paper base material may be, for example, 20 μm or more and 500 μm or less.

Generally, as a method for producing a paper base material, the above-mentioned pulp, water, and a paper material prepared by adding a filler or other chemicals as necessary are sprayed onto the wire of a paper machine, and a wire part is used. After dehydration in the press part, water extraction in the press part, and drying in the dryer part, a size press that gives strength and water resistance to the paper as needed, and a calendar process that smoothes the unevenness of the surface of the paper are applied to make the paper and finish it. The paper is wound up and finished to the specified winding size to complete the process. Further, in order to impart paper strength and water resistance to the paper, chemicals such as polyvinyl alcohol (PVA), starch, and surface sizing agent may be used alone or in combination of two or more as appropriate. The production of the paper base material in the present embodiment is not limited to this.

<Manufacturing method of raw material sheet>
As a method for producing the raw material sheet of the present embodiment, for example, it can be produced by the method shown below.
That is, in one embodiment, the present invention comprises a thermoplastic resin layer forming step of forming a thermoplastic resin layer on at least one surface of a paper base material and the paper base material after the thermoplastic resin layer forming step. After the ink coating portion forming step of applying the above-mentioned ink to the surface on which the thermoplastic resin layer is formed and drying to form the ink coating portion, and the ink coating portion forming step, the thermoplastic resin layer is foamed. Provided is a method for producing a raw material sheet, which comprises a foaming step of forming a foamed layer usually composed of a foamed portion and a printed foamed portion.

According to the manufacturing method of the present embodiment, it is possible to obtain a raw material sheet having a smooth printed surface and excellent heat insulating properties and design properties.
Hereinafter, each step will be described in detail.

[Thermoplastic resin layer forming process]
First, a thermoplastic resin layer is formed on at least one side of the paper base material.
The method for forming the thermoplastic resin layer is not particularly limited, and for example, if the thermoplastic resin layer is laminated by appropriately using a method such as an extrusion laminating method, a wet laminating method, a dry laminating method, or the like, which is bonded to a pre-filmed material. Good. Above all, as a method for forming the thermoplastic resin layer, the extrusion laminating method is preferable from the viewpoint of adhesion to the paper base material, foamability and the like. In the extruded laminate, for example, a thermoplastic resin layer is extruded from a T-die in the form of a molten resin film on a surface coated with a foaming accelerator of a paper base material, and cooled between a cooling roll and a nip roll facing the same. It is a method of crimping while crimping. In extruded laminating, operating conditions such as resin melting temperature and laminating speed may be appropriately set depending on the type of resin used and the apparatus, and are not particularly limited. Generally, for example, the melting temperature is 200 ° C. or higher and 350 ° C. or lower and the laminating speed. Is 50 m / min or more and 200 m / min or less. Further, it is preferable to use a nip roll having a hardness of 70 degrees or more (JIS K-6253) and perform pressing and crimping at a linear pressure of 15 kgf / cm or more.

If necessary, corona treatment, ozone treatment, or the like may be performed in order to improve the adhesiveness of the paper base material or the thermoplastic resin.

The thickness of the thermoplastic resin layer (foamed thermoplastic resin layer before heating) is sufficient to impart desired heat insulating properties when the foamed layer (foamed thermoplastic resin layer) is formed after heating. If it is good, it is not particularly limited, but for example, it may be 20 μm or more and 90 μm or less.

The thickness of the non-foamed thermoplastic resin layer before heating may be a thickness sufficient to prevent the evaporation of evaporated water, for example, 20 μm or more and 50 μm or less.

[Ink coating part forming process]
Next, ink is applied onto the formed thermoplastic resin layer to form an ink-coated portion.
As the ink, the same ink as those exemplified in the above (ink) may be used.
The method of applying the ink on the thermoplastic resin layer is not particularly limited, and examples thereof include a gravure printing method and a flexographic printing method.

[Foaming process]
Next, the thermoplastic resin layer is heat-treated to foam the thermoplastic resin layer to form a foamed layer usually composed of a foamed portion and a printed foamed portion.

The heating temperature and heating time vary depending on the type of paper substrate and thermoplastic resin used, and the optimum combination of heating temperature and heating time for the thermoplastic resin to be used can be appropriately determined. A temperature slightly higher than the melting point of the foaming thermoplastic resin (melting point + 5 ° C or higher and 30 ° C or lower) is suitable, and generally, the heating temperature is 110 ° C or higher and 200 ° C or lower, and the heating time is 1 minute or higher and 6 minutes or lower. is there. The heating means is not particularly limited, and any means such as hot air, electric heating, and an electron beam can be used. Mass production can be carried out at low cost by heating with hot air, electric heat, or the like in a tunnel provided with a means for transporting by a conveyor.

<Use>
The raw material sheet of the present embodiment is used for a paper product having heat insulating properties and a smooth printed surface, and specifically, for example, a foamable paper cup, a foamable paper container, a pamphlet, and a fancy paper. , Wrapping paper, wallpaper, etc.

[Foam paper container]
In one embodiment, the present invention provides an effervescent paper container made of the above-mentioned raw material sheet.

The foamable paper container of the present embodiment has a smooth printed surface, heat is not easily transferred to the hand, and has excellent heat insulating properties in practical use.

The foamable paper container of the present embodiment can be manufactured by, for example, the following method.
First, the raw material sheet is unwound from the take-up roll. Next, the blank for the body member and the blank for the bottom plate member are punched out from the raw material sheet and assembled in the shape of a container with a regular cup molding machine. Here, the foamed thermoplastic resin layer may be present on either one or both of the outer wall surface side and the inner wall surface side of the body member, and the heat insulating property, the touch, the appearance aesthetics, and the like may be appropriately determined as desired. However, when the inside of the container is a foamed surface, the foamed resin may be damaged by chopsticks, a fork, etc. and enter the mouth when eating or drinking, so it is preferable that the foamed resin exists on the outer wall surface side. Therefore, for example, the body member is assembled so that the foamed thermoplastic resin layer faces the outside of the container and the non-foamed thermoplastic resin layer faces the inside of the container. As the bottom plate member, a paper substrate having a non-foamed thermoplastic resin layer provided on at least one surface on the inner surface side of the container is preferably used. This is to prevent the permeation of liquids and the like into the paper. The thermoplastic resin used for the bottom plate member may be the same as or different from the body member, and the laminating method may be the extruded laminating method, the wet laminating method, the dry laminating method, or the like, which is previously made into a film. A suitable method can be used as appropriate.

For cup noodles and the like that are left to stand for a while after injecting hot water, it is effective to provide a foamed thermoplastic resin layer on the bottom member in order to prevent heat dissipation from the bottom surface of the container. Especially, it is preferable for outdoor use, winter and cold regions. Further, as the lid material, a material having a foamed thermoplastic resin layer may be used as well.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[Example 1] Production of foamable paper sheet ^{Low density on one side of a paper substrate of 280 g / m 2} (thickness 310 μm, density 0.90 g / cm ³ , chemical pulp 100%, water content 7.8%) Polyethylene (brand name: LC701, density 0.918 g / cm ³ , melting point 106 ° C., manufactured by Japan Polyethylene Corporation) was extruded and laminated to a thickness of 50 μm. Medium density polyethylene (brand name: LW04, density 0.940 g / cm ³ , melting point 131 ° C.) manufactured by Tosoh Corporation was extruded and laminated on the opposite surface of the paper substrate to a thickness of 40 μm. On this low-density polyethylene laminated film surface, each color of ink A, which is the blending ratio shown in Table 1 below, is used, and a gravure auto-purfer (printing tester) (printing cylinder plate type: engraving) is performed according to each printing pattern shown in Table 2. (Helio) 175-line solid) was used for gravure printing. After printing, it was placed in an oven and heated at 120 ° C. for 5 minutes for foaming. Table 2 shows the foam thickness in each ink-coated portion.

[Example 2] Production of foamable paper sheet 280 g / m ² (thickness 310 μm, density 0.90 g / cm ³ , chemical pulp 100%, water content 7.2%) paper substrate, and the table below. By the same method as in Example 1 except that each color of ink B, which is the blending ratio shown in 1, was used, and gravure printing (actual machine) (printing cylinder plate type: engraving (helio) 150-line solid) was used. , Manufactured foamed paper sheets. Table 2 shows the foam thickness in each ink-coated portion.

[Example 3] Manufacture of foamable paper sheet Each color of ink C, which is the blending ratio shown in Table 1 below, was used, and a gravure proofing machine (printing tester) (printing cylinder plate type: engraving (helio) 150). A foamable paper sheet was produced by the same method as in Example 1 except that the line solid) was used. Table 2 shows the foam thickness in each ink-coated portion.

[Example 4] Production of foamable paper sheet A foamable paper sheet was produced by the same method as in Example 1 except that each color of ink D, which is the blending ratio shown in Table 1 below, was used. .. Table 3 shows the foam thickness in each ink-coated portion.

[Reference Example 1] Production of Foamable Paper Sheet The same method as in Example 1 except that an ink containing a urethane resin and a vinyl chloride / vinyl acetate copolymer (manufactured by Toyo Ink Co., Ltd.) was used as the binder resin. To produce a foamable paper sheet. Table 3 shows the foam thickness in each ink-coated portion. In Table 3, the reason why the total amounts of the binder resin, silicon dioxide, the colorant, and the solvent are not 100% is that they contain other additives.

From Examples 1 to 4, the higher the content of the urethane resin in the ink, the larger the foam thickness and the lower the foam suppression rate.
Further, the print layer using the inks A and B containing silicon dioxide tended to have a larger foam thickness and a lower foam suppression rate than the print layer using the inks C and D not containing silicon dioxide.
Further, the ink A had the same foam thickness and foam suppression rate as the conventional ink containing chloride.

From the above, it was shown that the foamable paper sheet obtained from the raw material sheet of the present invention has a smooth printed layer surface and is excellent in appearance.

According to the present invention, there is provided a raw material sheet containing an ink having a small impact on the environment, a foamable paper product having a smooth print layer surface and an excellent appearance, and a foamable paper container made of the raw material sheet. be able to.

A ... Ink non-painted area, B ... Ink-painted area, X ... Foam thickness in ink non-painted part (usually foamed part 4), Y ... Foam thickness in one-layer ink-painted part, Z ... In two-layer ink-painted part Foam thickness, 1 ... printing layer, 1a ... first ink coating part, 1b ... second ink coating part, 2a ... non-foamed thermoplastic resin layer, 2b ... foamed thermoplastic resin layer, 2b'... foamed layer (heating) Later foamed thermoplastic resin layer), 3 ... Paper substrate, 4 ... Normal foamed portion, 5 ... Printed foamed portion, 5a ... First printed foamed portion, 5b ... Second printed foamed portion, 10 ... Before foaming Raw material sheet, 20 ... Raw material sheet after foaming.

Claims (6)

A raw material sheet used for foamable paper products.
It is composed of a paper base material provided with a foam layer formed by heating a thermoplastic resin layer having at least one layer or more of an ink-coated portion on one side thereof.
The ink contains a colorant and a binder resin and is substantially free of chlorides.
Wherein the binder resin is seen containing urethane resin, or a urethane resin and nitrocellulose,
A raw material sheet having a glass transition point of the urethane resin of −20 ° C. or higher and 0 ° C. or lower. The raw material sheet according to claim 1, wherein the glass transition point of the urethane resin is −20 ° C. or higher and −12 ° C. or lower. The raw material sheet according to claim 1 or 2, wherein the urethane-based resin is a polyether urethane resin. The raw material sheet according to any one of claims 1 to 3, wherein the content of the urethane-based resin in the resin solid content of the binder resin is 50% or more. The raw material sheet according to any one of claims 1 to 4, wherein the binder resin further contains silicon dioxide. A foamable paper container comprising the raw material sheet according to any one of claims 1 to 5.

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