JP2018167864A - Raw material sheet and foaming-paper-made container - Google Patents

Abstract

The present invention provides a raw material sheet that contains an ink that has little influence on the environment, has a smooth printed layer surface, and has an excellent appearance, and a foamable paper container using the raw material sheet.
The present invention is a raw material sheet used for a foamable paper product, comprising a paper base material provided with a foamed layer formed by heating a thermoplastic resin layer having at least one ink coating portion on one side. The ink contains a colorant and a binder resin and is substantially free of chloride, and the binder resin contains a urethane resin, or a urethane resin and nitrified cotton. The foamable paper container of the present invention comprises the raw material sheet.
[Selection figure] None

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 formed by laminating low density polyethylene on one side of a base paper and high density or medium density polyethylene on one side of the base paper, and heating in an oven. On the surface of the low density polyethylene, there is a printing layer including a printing 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 printed layer contains a polyamide resin or the like and a cellulose derivative as a binder component. The ink remarkably suppresses foaming of low density polyethylene, and in the printed part and the non-printed part of the printed layer or in the printed part and the overprinted part further printed on the printed part, Differences occur in the thickness of low density polyethylene. Thereby, the said printing part or the said overcoat part becomes a recessed part, a level | step difference arises, and it has the subject that printing becomes unclear.

  As an ink for improving the unevenness of the printed layer surface, 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 vinyl chloride / vinyl acetate copolymer, the mixing ratio of urethane resin: vinyl chloride / vinyl acetate copolymer is 50:50 to 99: 1, and the elongation percentage of the binder resin An ink is disclosed in which is from 400% to 3,000%.

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.

  Accordingly, the present invention has been made in view of the above circumstances, and includes a raw material sheet that contains an ink that has little influence on the environment, a foamed paper product that has a smooth printing layer surface and excellent appearance, and the raw material sheet. A foamable paper container using the above is provided.

  As a result of diligent research to solve the above-mentioned problems, the present inventors have found that ink containing substantially no chloride can be obtained by using nitrified cotton instead of chloride as necessary for the ink composition components. As a result, it was found that a foamable paper product having good foamability was obtained, 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, comprising a paper base material provided with a foam layer formed by heating a thermoplastic resin layer having at least one ink coating portion on one side, and the ink is colored A raw material sheet comprising an agent and a binder resin and substantially free of chloride, wherein the binder resin comprises a urethane resin, or a urethane resin and nitrified cotton.
[2] The raw material sheet according to [1], wherein the urethane resin has a glass transition point of −20 ° C. or higher and 30 ° C. or lower.
[3] The raw material sheet according to [1] or [2], wherein the urethane resin is a polyether urethane resin.
[4] The raw material sheet according to any one of [1] to [3], wherein a content of the urethane resin in a 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 are provided a raw material sheet containing an ink that has little influence on the environment, a smooth printed layer surface and an excellent appearance, and a foamable paper container using the raw material sheet. can do.

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

  Hereinafter, a mode for carrying out the present invention (hereinafter, simply referred to as “the present embodiment”) will be described in detail. The following embodiment 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 implemented with appropriate modifications 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, comprising a foamed layer formed by heating a thermoplastic resin layer having at least one ink coating portion on one side. Thus, a raw material sheet is provided in which the ink contains a colorant and a binder resin and substantially does not contain chloride, and the binder resin contains a urethane resin, or a urethane resin and nitrified cotton.

  According to the raw material sheet of this embodiment, a foamable paper product having a smooth printing layer surface and excellent appearance can be obtained. Moreover, since the ink coating part with which the raw material sheet | seat of this embodiment is provided does not contain a chloride substantially, there are few environmental impacts and it is more suitable for the use by food use.

  In the present specification, “substantially free of chloride” means a state containing no chloride at all or containing a very small amount of chloride that 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 the raw material sheet before being heated and foamed, and FIG. 1B shows the raw material sheet after being heated and foamed.
The raw material sheet 10 before foaming of the present embodiment has an ink non-coating region A and an ink coating region B that are adjacently arranged in plan view, and includes a non-foamed thermoplastic resin layer 2a and a paper base 3 The foamed thermoplastic resin layer 2b and the printing layer 1 (the first ink coating portion 1a and the second ink coating portion 1b) are laminated in this order.
Moreover, in the raw material sheet 20 after foaming of the present embodiment, the foam layer 2b ′ heats the foamed thermoplastic resin 2b having the printing layer 1 (the first ink coating portion 1a and the second ink coating portion 1b). It consists of the normal foaming part 4 which exists in the ink non-coating area | region A, and the printing foaming part 5 which exists in the ink coating area | region B. By the ink coating, the foaming of the printing foamed portion 5 is somewhat suppressed as compared with the normal foamed portion 4. Furthermore, the printing foaming part 5 includes a first printing foaming part 5a formed in a region where the first ink coating part is exposed on the surface, that is, one layer of the ink painting part, and a second ink painting part. Are exposed on the surface, that is, the second printed foamed portion 5b formed in the two-layer ink coating portion.

In the raw material sheet 20 after foaming of the present embodiment, the foam thickness in the non-ink-painted portion (normally foamed portion 4) is X, and the foam thickness in the one-layer ink-painted portion (first print foamed portion 5a) is Y. The foaming inhibition 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) × 100 (1)
When the foaming suppression rate is within the above range, the boundary between the ink non-coating region and the ink coating region becomes a smooth printed matter, and the printing can be visually recognized clearly.

For X and Y, an average value of measured values of the foam thickness in the non-ink-painted portion (normally foamed portion 4) or the one-layer ink-coated portion (first printed foamed portion 5a) may be used.
1A and 1B exemplify a raw material sheet having a two-layer ink coating portion. However, the foam coating thickness in ink coating portions of two or more layers, for example, three layers, four layers, etc., is also applied to each layer. The foaming suppression rate may be calculated by measuring the foaming thickness at the part and applying the numerical value to the above formula (1) using the average value.
For example, in FIG. 1B, when the foam thickness in the two-layer ink coating portion is Z, the foam suppression rate may be calculated using Z instead of Y in the above formula (1). That is, the foaming suppression rate in the second print foaming part 5b with respect to the normal foaming part 4 is represented by the following formula (2).
Foam suppression rate (%) = (1−Z / X) × 100 (2)

  Moreover, the color of the ink used for a 1st ink coating part and a 2nd ink coating part may be the same color, and a different color may be sufficient as it.

Further, in the raw material sheet 20 after foaming of the present embodiment, the foam thickness in the one-layer ink coating portion (first printing foam portion) is Y, and the two-layer ink coating portion (second printing foam portion). When the foam thickness in Z is Z, the foam inhibition 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) × 100 (3)
When the foaming suppression rate is within the above range, the surface of the printing layer is smooth, and printing can be visually recognized clearly.

  The raw material sheet of the present invention is not limited to that shown in FIGS. 1A to 1B, and a part of the configuration shown in FIGS. 1A to 1B is changed or deleted within a range not impairing the effects of the present invention. In addition, another configuration may be added to what has been described so far.

  For example, the raw material sheet shown in FIGS. 1A to 1B may include two or more layers, for example, three or four layers of ink coating portions. Especially, it is preferable that an ink coating part is 2 layers or more and 8 layers or less.

  Moreover, in the raw material sheet | seat shown to FIG. 1A-FIG. 1B, the ink was apply | coated to the whole surface and it may be covered with the printing layer, ie, the ink non-coating part may not be provided.

  Moreover, in the raw material sheet | seat shown to FIG. 1A-FIG. 1B, a foamed thermoplastic resin layer may be provided on both surfaces.

<Constituent materials>
The material which comprises the raw material sheet | seat of this embodiment is demonstrated below.

[Print layer]
In the raw material sheet of this embodiment, it is preferable that the thickness after drying of the ink coating part before heating is 2 μm or less per layer. By being 2 μm or less, it is possible to obtain a smooth printed surface without suppressing foaming.
When the ink coating part is, for example, two layers, the printing layer after drying is preferably 4 μm or less. For example, when the ink coating part is, for example, three layers, the printing layer after drying is 6 μm or less. It is preferable.

(ink)
The ink used for the printing layer of this embodiment is obtained by adding a solvent to the structure of the dried ink coating part. That is, the ink contains a colorant, a binder resin, and a solvent.
Moreover, since the ink used for the printing layer of this embodiment does not contain chloride substantially, there is little environmental impact.

Colorant The colorant need only be substantially free of chloride, and may be an inorganic colorant or an organic colorant.
Examples of inorganic colorants 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.
From the viewpoint of coloring power, hiding power, chemical resistance, and weather resistance, titanium oxide is preferable for the white colorant, and titanium oxide having a basic pigment surface is more preferable. Aluminum is in the form of powder or paste, but is preferably used in the form of paste from the viewpoint of handling and safety, and whether to use leafing or non-leafing is appropriately selected from the viewpoint of brightness and concentration.
Barium sulfate, calcium carbonate, aluminum hydroxide, talc, clay and kaolin are called extender pigments and are used as extenders 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, and recording agents. Examples thereof include azo, phthalocyanine, anthraquinone, perylene, perinone, quinacridone, thioindigo, dioxazine, isoindolinone, quinophthalone, azomethine azo, dictopyrrolopyrrole, and isoindoline.
However, colorants 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 is generally 50% by weight or less based on the total weight of the ink, and the above upper limit value. By being below, it becomes content of the coloring agent from which a required meat concentration is obtained.

When the ink used in the printing layer of the present embodiment is white, the content of the white pigment is 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. As a result, the content of the pigment can be obtained to obtain the required concentration of the flesh. From the viewpoint of concealability, pigment concentration, and light resistance, the white pigment is preferably titanium dioxide.
Further, when the ink used in the present embodiment is colored, examples of the colored pigment included include colored organic pigments and colored inorganic pigments such as Bengala, bitumen, ultramarine blue, carbon black, and graphite. . From the viewpoint of color developability and light resistance, the colored pigment is preferably an organic pigment. The content of the colored pigment is generally 10% by weight or more and 30% by weight or less, based on the total weight of the ink. It becomes quantity.

Binder resin The binder resin contains a urethane resin, or a urethane resin and nitrified cotton.
When the ink used for the printing layer of this embodiment is white, since the dispersibility of a pigment is excellent, the ink should just contain only urethane type resin as binder resin. On the other hand, when the ink used in this embodiment is colored, in order to improve the dispersibility of the pigment, the ink preferably contains nitrified cotton in addition to the urethane resin as a binder resin.

O Urethane resin The urethane 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. Generation | occurrence | production of blocking is suppressed when the glass transition point of the said urethane-type resin is more than the said lower limit, and suppression of foaming can be suppressed by being below the said upper limit.
In general, “blocking” means that the surface of the raw material sheet having the printed layer and the surface on the opposite side stick to each other when printing, drying, and winding of the ink are performed.

  In the present specification, the “urethane resin” means a urethane resin in a broad sense including a modified urethane resin such as a general urethane resin or a urethane urea resin conventionally used in the art. In addition, the urethane resin used as the binder resin in the present embodiment is not particularly limited depending on the manufacturing method, and various urethane resins obtained by applying known or well-known methods related to the urethane resin. I just need it. Specifically, for example, urethane resins such as polyether urethane resins (the above-mentioned “general urethane resins”), polyurethane urea resins and the like can be mentioned. Among these, as the urethane resin used as the binder resin in the present embodiment, a polyether urethane resin is preferable.

-Urethane resin The said urethane resin can be manufactured by making a polyol compound and organic diisocyanate react.

1. Polyol compound Examples of the polyol compound used for the production of the urethane resin include various known polyols as shown below.
(1) Polyether polyols such as polymers or copolymers such as ethylene oxide, propylene oxide, and tetrahydrofuran;
(2) Other polycarbonate diols, polybutadiene glycols, glycols obtained by adding bisphenol A ethylene oxide or propylene oxide;
(3) Dimer diols.
These various polyols may be used independently and may use 2 or more types together.

  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, a range of 500 to 10,000 is usually preferable, and a range of 500 to 6,000 is more preferable. When the number average molecular weight is not less than the above lower limit, the solubility does not decrease and the printability can be prevented from decreasing. Moreover, it can prevent that drying property and blocking resistance fall because a number average molecular weight is below the said upper limit.

2. Organic Diisocyanate The organic diisocyanate used in the production of the urethane resin may be various known aromatic, aliphatic, or alicyclic diisocyanates. Specifically, for example, 1,5-naphthylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyldimethylmethane diisocyanate, 4,4′-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 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, norbornane diisocyanate, m-tetramethylxylylene diisocyanate, and the carboxyl group of dimer acid were converted to isocyanate groups. Examples include dimer isocyanate.

3. Manufacturing method The manufacturing method of the said urethane resin may be a conventionally well-known or well-known method, and is not restrict | limited in particular. For example, when the polyol compound and the organic diisocyanate are reacted, the other conditions are not limited except that the organic diisocyanate is used excessively with respect to the polyol compound. In the urethane resin synthesis method, it is preferable to set the molar equivalent ratio of isocyanate group / hydroxyl group within the range of 1.2 / 1 to 3/1. It can prevent that the urethane resin obtained becomes weak because the molar equivalent ratio of isocyanate group / hydroxyl group is more than the said lower limit. On the other hand, when the molar equivalent ratio of isocyanate group / hydroxyl group is not more than the above upper limit, an increase in viscosity during the production of the urethane resin can be suppressed, and gelation can be prevented from occurring during the reaction.
The temperature of the polyurethane reaction during the production of the 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 performed in a solvent or in a solvent-free atmosphere. In the case of using a solvent, from the viewpoint of controlling the reaction temperature, viscosity, and side reaction, the same ones as exemplified in “Solvent” described later can be appropriately selected.
Moreover, when performing the said polyurethane-ized reaction in solvent-free atmosphere, in order to obtain a uniform urethane resin, it is preferable to carry out by raising temperature to the extent which can fully stir and lowering | hanging a viscosity. The reaction time for the polyurethane reaction is preferably 10 minutes to 5 hours. 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 prepared 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 converting the amine compound or amide compound into a chain extender and a reaction terminator. And a resin obtained by introducing a urea bond into the urethane resin.

1. Chain extender Examples of the chain extender that can be used for introducing 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, dimer amine obtained by converting the carboxyl group of dimer acid into an amino group, and the like. It is done. These may be used alone or in combination of two or more.

2. Reaction Terminator Examples of the reaction terminator include aliphatic amine compounds or fatty acid amide compounds having a C8 or more and C22 or less long chain alkyl group.
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, behenic acid amide, oleic acid amide, erucic acid amide, linoleic acid amide, and linolenic acid. Examples include acid amides. These may be used alone or in combination of two or more.

3. Production method The production method of the urethane resin is as described above. Furthermore, it does not specifically limit as a manufacturing method which introduce | transduces a urea bond in a urethane resin.
For example, when the number of free isocyanate groups present at both ends of the urethane resin is 1, the total number of amino groups in the chain extender and reaction terminator used is in the range of 0.5 to 1.3. It is preferable to do. When the total number of the amino groups is equal to or more than the lower limit, it is possible to sufficiently obtain the effect of improving the drying property, the blocking resistance, and the coating film strength. On the other hand, when the total number of amino groups is not more than the above upper limit, it is possible to prevent the odor from remaining in the printed layer without leaving the chain extender and the reaction terminator unreacted.

The resin solid content of the binder resin preferably contains 50% or more of the urethane resin, more preferably 60% or more, further preferably 70% or more, and more preferably 80% or more. Particularly preferred, it is most preferred to contain 90% or more.
When the content of the urethane-based resin in the binder resin is within the above range, the raw material sheet having a smooth printing surface can be obtained without substantially suppressing the foaming of the thermoplastic resin.

○ Nitrated 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 a hydroxyl group in the cellulose is substituted with a nitrate group.
In general, nitrified cotton has high coating strength, elastic modulus, and surface hardness, so it is used for various applications. Further, solubility can be selected by nitrogen content, and solution viscosity can be selected by degree of polymerization.
In this specification, the “nitrogen content” means the weight% of nitrogen atoms in the resin, and becomes a larger value as the amount of cellulose hydroxyl groups substituted with nitrate groups increases. In the case of industrial nitrified cotton, those having a nitrogen content of 10.7 or more and 12.2 or less are common. The nitrified cotton used in this embodiment may be a low nitrogen content type called L cotton or L type having a nitrogen content of 10.7 or more and 11.5 or less, and the nitrogen content is 11.5 or more. It may be a high nitrogen content type called H cotton or H type which is 12.2 or less, and there is no special limitation.
Moreover, the average degree of polymerization of the nitrified cotton used in the present embodiment may be, for example, 30 or more and 150 or less. When the average degree of polymerization of the nitrified cotton is at least the above lower limit, the toughness of the film can be secured, and the ink has excellent alcohol bleed resistance and blocking resistance. On the other hand, when the average degree of polymerization of the nitrified cotton resin is not more than the above upper limit, it is possible to prevent the viscosity of the nitrified cotton solution or the ink from increasing.

When the ink is colored, the resin solid content of the binder resin preferably contains 50% or less nitrified cotton, more preferably 10% or more and 40% or less, and more preferably 20% or more and 30% or less. Further preferred.
When the content of nitrified 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. In addition, cracking of the ink surface can be prevented in the ink coating portion of the raw material sheet after foaming.

-Content of binder resin In this embodiment, it is preferable that content of binder resin is 15 to 25 weight% on the basis of the total mass of ink. When the content of the binder resin is equal to or higher than the lower limit, an appropriate ink viscosity is obtained, and when the content is equal to or lower than the upper limit, the ink fluidity is prevented from being lowered, and ink production and printing are performed. Work efficiency can be increased.

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

Extender Pigment The ink used in the printing layer of the present embodiment preferably further includes an extender pigment. By including the extender, an ink having better foamability can be obtained.

Examples of the extender pigment include silicon dioxide, talc, kaolin, and magnesium oxide. Among them, the extender pigment contained in the ink in the present embodiment is preferably silicon dioxide.
The silicon dioxide may be, for example, a compound known as “synthetic silica” produced by a known method. A typical method for producing synthetic silica is a wet method in which ultra-fine hydrous silicic acid is produced by reacting sodium silicate with acid from high-purity silica sand, or combustion hydrolysis of 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 synthesis method, and examples thereof include untreated silicon dioxide (untreated silica).
The particle diameter 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 diameter equal to or greater than the above lower limit, it is possible to prevent the viscosity of the ink from being increased and to prevent the ink state from being lowered. In addition, by using silicon dioxide having a particle size equal to or smaller than the upper limit, it is possible to prevent the ink film from following poor foaming with respect to foaming of a low-melting resin film used as a foamed thermoplastic resin during heat treatment during container production. be able to.

  The particle diameter 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 an average particle diameter obtained by measurement using a 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 less based on the total mass of the ink. It is more preferable that the amount is not more than mass%. 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 includes auxiliary agents (for example, 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 anti-foaming agents, leveling agents, pigment dispersants, plasticizers, and other various ink additives.

[Foamed thermoplastic resin layer]
In the raw material sheet of the present embodiment, the foam layer is formed by heating the thermoplastic resin layer. That is, the foam 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 foamed, and either a crystalline resin or an amorphous resin can be used. . Examples of the crystalline resin include polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; polyester resins, polyamide, polyacetal, and PPS resins. Examples of the amorphous resin include polystyrene, polyvinyl chloride, ABS resin, acrylic resin, modified PPE, polycarbonate, polyurethane, polyvinyl acetate, and amorphous polyethylene terephthalate (PET). The melting point of these thermoplastic resins is preferably about 80 ° C. or higher and 120 ° C. or lower. These thermoplastic resins may be a single resin or a plurality of resins, but are preferably a single layer from the viewpoint of foamability.

Among these, polyethylene is preferable as the thermoplastic resin used for the foamed thermoplastic resin layer because of its excellent laminating property and foamability. Polyethylene is roughly 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.
As for the melting point, 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 provide at least one of desired heat insulating properties and design properties. In the first printing foam portion and the second printing foam portion, it may be 0.01 mm or more and 4 mm or less, and in the foam suppression portion, it may be 0 mm or more and 1 mm or less.

[Non-foamed thermoplastic resin layer]
In the raw material sheet of this embodiment, in order to increase the foaming efficiency, the opposite wall surface side of the wall surface having the foamed thermoplastic resin layer of the trunk member is made of a thermoplastic resin having a melting point higher than that of the foamed thermoplastic resin layer and is subjected to heat treatment. It is preferable to coat with a thermoplastic resin layer (non-foamed thermoplastic resin layer) that does not foam when it is applied, an aluminum foil or the like. If one side of the paper substrate is ground (not laminated or coated), the moisture in the paper will evaporate from the uncoated surface to the atmosphere during heat treatment. It becomes difficult to foam. Therefore, by providing such a coating layer, 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 of the body member, the filling liquid or the like will penetrate into the paper. Is preferable.

  The thermoplastic resin used for the non-foamed thermoplastic resin layer of the raw material sheet of this embodiment may be the same as or different from the foamed thermoplastic resin layer. In the case of the same, a difference in the melting point can be caused by making a difference in density. 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 thermoplastic resin layers of the foamed thermoplastic resin layer and the non-foamed thermoplastic resin layer is preferably 5 ° C. or more. The melting point of the thermoplastic resin of the non-foamed thermoplastic resin layer is a melting point during heating. There is no particular limitation as long as diffusion of evaporated water can be prevented, but 125 ° C. or higher is preferable.

[Paper base]
As the paper base material used for the raw material sheet of the present embodiment, for example, chemical pulp obtained from wood, mechanical pulp is mainly used, and non-wood pulp such as kenaf and bamboo is blended as necessary, usually. The paper base material obtained by papermaking by the papermaking process of this is mentioned, It is not limited to this. Especially, as a paper base material used for the raw material sheet | seat of this embodiment, it is preferable that it contains a chemical pulp. Compared to the case of using mechanical pulp because it contains chemical pulp, it is easy to increase the density and suppress yellowing when exposed to light for a long time or when stored at high temperature for a long time. In addition, the strength and rigidity when assumed to be used for a container are increased.

The blending ratio of the chemical pulp to the total raw material pulp used for the paper base is preferably 80% by weight or more, more preferably 90% by weight or more, and further preferably 95% by weight or more.
In addition, it is preferable that chemical pulp contains a large amount of fibers derived from coniferous trees because of its high foaming property.
5% or more is preferable, the compounding rate of the chemical pulp derived from the conifer with respect to all the raw material pulp used for a paper base material is more preferable, 10% or more is more preferable, and 20% or more is further more preferable.

The base paper basis weight of the paper substrate may be, for example, 25 g / m ² or more and 500 g / m ² or less. Also, when using a raw material sheet of the present embodiment to the container, the base paper grammage of the paper substrate may if considering the foaming example 30 g / m ² or more 400 g / m ² or less.
When the base paper basis weight of the raw material sheet of the present embodiment is equal to or more than the lower limit value, it is possible to sufficiently ensure the water amount necessary for imparting heat insulation and design properties by foaming. Moreover, when the base paper basis weight of the raw material sheet of this embodiment is equal to or less 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 freeness (“Canadian Standard” freeness; 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, the water vapor hardly penetrates inside the paper base material, and the water vapor hardly escapes from the end surface of the paper base material, so that the foam thickness is increased. When the CSF of the pulp is 200 mL or more, the power consumption for beating the pulp to lower the freeness is not increased, and the cost is excellent. In addition, it is possible to ease the facility response for increasing 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 further preferably 0.8 g / cm ³ or more.
The thickness of the paper substrate may be, for example, 20 μm or more and 500 μm or less.

  As a method for producing a paper substrate, generally, the above 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 obtained. After dewatering, pressing in the press part, drying in the dryer part, and then, if necessary, the paper is made by applying a size press that gives the paper strength and water resistance, and a calendar process that adjusts the unevenness of the paper surface. The paper is rolled up and finished to a predetermined winding dimension. Further, in order to impart paper strength and water resistance to paper, chemicals such as polyvinyl alcohol (PVA), starch, and surface sizing agent may be used alone or in appropriate combination of two or more. In addition, manufacture of the paper base material in this embodiment is not limited to this.

<Method for manufacturing raw material sheet>
As a manufacturing method of the raw material sheet of this embodiment, it can manufacture by the method etc. which are shown below, for example.
That is, in one embodiment, the present invention includes a thermoplastic resin layer forming step of forming a thermoplastic resin layer on at least one surface of a paper substrate, and the paper substrate after the thermoplastic resin layer forming step, The above-mentioned ink is applied to the surface on which the thermoplastic resin layer is formed and dried to form an ink coating portion, and after the ink coating portion formation step, the thermoplastic resin layer is foamed. And a foaming step of forming a foamed layer composed of a normal foaming part and a printing foaming part.

According to the manufacturing method of the present embodiment, a raw material sheet having a smooth printing surface and excellent heat insulation and design can be obtained.
Hereinafter, each step will be described in detail.

[Thermoplastic resin layer forming step]
First, a thermoplastic resin layer is formed on at least one side of a paper substrate.
The method for forming the thermoplastic resin layer is not particularly limited. For example, if a method of laminating with a film-like one such as an extrusion laminating method, a wet laminating method, or a dry laminating method is appropriately used for lamination. Good. Among these, as a method for forming the thermoplastic resin layer, an extrusion laminating method is preferable from the viewpoints of adhesion to a paper base material, foamability, and the like. For example, extrusion lamination is performed by extruding a thermoplastic resin layer from a T-die in the form of a molten resin film onto a surface of a paper substrate on which a foaming accelerator has been applied, and cooling between a cooling roll and a nip roll facing it. It is a method of crimping while. In extrusion lamination, the operating conditions such as the melting temperature and lamination speed of the resin are not particularly limited as long as they are appropriately set depending on the type and apparatus of the resin to be used. 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 pressing and pressure bonding with a linear pressure of 15 kgf / cm or more.

  Corona treatment, ozone treatment, and the like may be performed as necessary to improve the adhesion of the paper base material and the thermoplastic resin.

  The thickness of the thermoplastic resin layer (foamed thermoplastic resin layer before heating) is sufficient to provide desired heat insulation when the foamed layer (foamed thermoplastic resin layer) is formed after heating. However, it may be, for example, 20 μm or more and 90 μm or less.

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

[Ink coating part forming process]
Next, ink is applied on the formed thermoplastic resin layer to form an ink coating portion.
As the ink, the same ink as exemplified in the above (ink) may be used.
The method for 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, thereby forming a foamed layer composed of a normal foamed part and a printed foamed part.

  The heating temperature and heating time vary depending on the type of paper substrate and thermoplastic resin to be used, and the optimal 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. Generally, the heating temperature is 110 ° C. or higher and 200 ° C. or lower and the heating time is 1 minute or longer and 6 minutes or shorter. is there. A heating means is not specifically limited, For example, arbitrary means, such as a hot air, electric heating, and an electron beam, can be used. If it is heated by hot air or electric heat in a tunnel equipped with a conveyor means, mass production can be performed at low cost.

<Application>
The raw material sheet of this embodiment is used for paper products having a heat insulating property and a smooth printing surface. Specifically, for example, a foamable paper cup, a foamable paper container, a brochure, and fancy paper. , Wrapping paper, wallpaper, etc.

[Foamed paper container]
In one embodiment, the present invention provides a foamable paper container comprising the raw material sheet described above.

  The foamable paper container of the present embodiment has a smooth printed surface, is difficult to transfer heat to the hand, and has excellent heat insulation in practical use.

The foamable paper container of this embodiment can be manufactured by the following method, for example.
First, a raw material sheet is fed out from a take-up roll. Next, a blank for a trunk member and a blank for a bottom plate member are punched out from the raw material sheet and assembled into a container shape by a conventional cup molding machine. Here, the foamed thermoplastic resin layer only needs to be present on one or both of the outer wall surface side and the inner wall surface side of the body member, and the heat insulation property, the touch, the appearance aesthetics, and the like may be appropriately determined as desired. However, when the inside of the container has a foamed surface, the foamed resin may be damaged by chopsticks, forks, or the like during food and drink, and may enter the mouth. 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 base material provided with a non-foamed thermoplastic resin layer on at least one side of the inner surface of the container is preferably used. This is to prevent penetration of liquid or the like into the paper. The thermoplastic resin used for the bottom plate member may be the same as or different from that of the body member, and the lamination method is not only the extrusion lamination method but also a pre-film-like one such as a wet lamination method or a dry lamination method. The method to combine can be used suitably.

  It is effective to provide a foamed thermoplastic resin layer on the bottom member of cup noodles or the like that are allowed to stand for a while after pouring hot water in order to prevent heat dissipation from the bottom of the container. In particular, it is preferable for outdoor use, winter and cold regions. Similarly, a lid member having a foamed thermoplastic resin layer may be used.

  EXAMPLES Hereinafter, although an Example is given and this invention is further explained in full detail, this invention is not limited to these Examples.

[Example 1] Production of foamable paper sheet 280 g / m ² (thickness 310 μm, density 0.90 g / cm ³ , chemical pulp 100%, moisture content 7.8%) Polyethylene (trade name: LC701, manufactured by Nippon Polyethylene Co., Ltd., density 0.918 g / cm ³ , melting point 106 ° C.) was extrusion 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 to a thickness of 40 μm on the opposite surface of the paper substrate. Gravure auto pull fur (printing tester) (printing cylinder plate type: engraving) according to each printing pattern shown in Table 2 using each color of ink A having the blending ratio shown in Table 1 below on the surface of this low density polyethylene laminate film (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 at each ink coating part.

[Example 2] Production of sheet of foamable paper 280 g / m ² (thickness 310 μm, density 0.90 g / cm ³ , chemical pulp 100%, moisture content 7.2%), paper base, and the following table In the same manner as in Example 1, except that each color of ink B having the blending ratio shown in 1 was used and gravure printing (actual machine) (printing cylinder plate type: engraving (Helio) 150 line solid) was used. A foamable paper sheet was produced. Table 2 shows the foam thickness at each ink coating part.

[Example 3] Manufacture of sheet made of foamable paper Each color of ink C having 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 in the same manner as in Example 1 except that (line solid) was used. Table 2 shows the foam thickness at each ink coating part.

[Example 4] Production of foamable paper sheet A foamable paper sheet was produced in the same manner as in Example 1 except that each color of ink D having the blending ratio shown in Table 1 below was used. . Table 3 shows the foam thickness at each ink coating part.

[Reference Example 1] Production of foamable paper sheet The same method as in Example 1 except that an ink containing urethane resin and vinyl chloride / vinyl acetate copolymer (manufactured by Toyo Ink Co., Ltd.) was used as the binder resin. Thus, a foamable paper sheet was produced. Table 3 shows the foam thickness at each ink coating part. In Table 3, the addition of the binder resin, silicon dioxide, colorant, and solvent does not result in 100% because it contains other additives.

From Examples 1 to 4, the greater the content of the urethane resin in the ink, the greater the foam thickness and the lower the foam suppression rate.
Moreover, the printing layer using the inks A and B containing silicon dioxide tended to have a larger foam thickness and lower foaming suppression rate than the printing layers using the inks C and D not containing silicon dioxide.
Ink A had the same foaming thickness and foaming suppression rate as conventional inks 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 excellent appearance.

  According to the present invention, there are provided a raw material sheet containing an ink that has little influence on the environment, a smooth printed layer surface and an excellent appearance, and a foamable paper container comprising the raw material sheet. be able to.

A: Ink non-coating area, B: Ink coating area, X: Foaming thickness in non-inking part (normally foaming part 4), Y: Foaming thickness in one ink coating part, Z ... In two ink coating parts Foam thickness, 1 ... printing layer, 1a ... first ink coating part, 1b ... second ink coating part, 2a ... non-foaming thermoplastic resin layer, 2b ... foaming thermoplastic resin layer, 2b '... foaming layer (heating 3) paper base material, 4 ... normal foaming part, 5 ... printing foaming part, 5a ... first printing foaming part, 5b ... second printing foaming part, 10 ... before foaming Raw material sheet, 20 ... Raw material sheet after foaming.

Claims (6)

A raw material sheet used for foamable paper products,
It consists of a paper substrate provided with a foamed layer formed by heating a thermoplastic resin layer having at least one layer of ink coating on one side,
The ink includes a colorant and a binder resin and is substantially free of chloride;
The raw material sheet, wherein the binder resin contains a urethane resin, or a urethane resin and nitrified cotton.   The raw material sheet according to claim 1, wherein a glass transition point of the urethane resin is −20 ° C. or higher and 30 ° C. or lower.   The raw material sheet according to claim 1, wherein the urethane resin is a polyether urethane resin.   The raw material sheet according to any one of claims 1 to 3, wherein a content of the urethane resin in a 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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