JP3108201B2 - Substrates for paper containers for cold drinks - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper laminate used as a base material for juice, beer, yogurt, ice cream, shaved ice, or as a disposable container for paper containers for cold foods and drinks.

[0002]

2. Description of the Related Art Paper containers used for cold foods and drinks use a paraffin-based composition as a water-repellent layer. There is a problem in that the container is deformed, and the paraffin-based composition is peeled off by the impact of a sharp part such as a spoon or a straw, and thus the durability of the water-repellent layer is required to be improved.

Further, used paper containers are coated with a non-biodegradable paraffinic composition on paper, so they do not decompose even when buried in soil. The water-repellent layer composition that biodegrades together with the paper is strongly demanded because it is very troublesome and requires labor and cost that the used paper container is immersed in an aqueous alkaline solution to separate the paraffin composition. I have.

[0004]

DISCLOSURE OF THE INVENTION The present invention relates to a conventional paper container for cold food and drink, which is a problem in use, when the paraffin-based composition layer is cracked by impact or by impact or friction. It solves the problem of reduced water resistance due to peeling, and also adds biodegradability to paper containers to prevent the accumulation of non-biodegradable substances in soil due to disposal of used containers, The purpose is to develop a base material for paper containers that is advantageous for preservation of paper.

[0005]

Means for Solving the Problems The present invention provides: [1] After preparing a prepolymer having a number average molecular weight of 5,000 or more, 0.1 to 0.1 part by weight of the prepolymer is used.
-5 parts by weight of the coupling agent were reacted at a temperature of 190
Melt viscosity at 3.5 ° C. and a shear rate of 100 (sec ⁻¹ ) is 3.5 × 10 ^{3 to} 4.0 × 10 ⁴ poises, and glycol and aliphatic dicarboxylic acid having melting points of 60 to 85 ° C. are main constituent units. A base material for paper containers for cold drinks, wherein the aliphatic polyester resin thus obtained is laminated on base paper, and [2] the aliphatic polyester resin is laminated on base paper at a resin temperature of 150 to 290 ° C. The above object has been achieved by developing the above-mentioned paper container base material for cold drinks and foods according to the above [1].

The aliphatic polyester referred to in the present invention is mainly composed of a polyester synthesized from a glycol and an aliphatic dicarboxylic acid or an acid anhydride thereof. This is obtained by synthesizing a relatively high molecular weight polyester prepolymer having a hydroxyl group and then coupling these prepolymers with a coupling agent.

Conventionally, a low molecular weight polyester prepolymer having a hydroxyl group at the terminal group and having a number average molecular weight of 2,000 to 2,500 is reacted with diisocyanate to form polyurethane, rubber, foam, paint, and adhesive. It is widely used as an agent.

[0008] However, the polyester prepolymer used for these polyurethane foams, paints and adhesives is a low molecular weight prepolymer having a number average molecular weight of 2,000 to 2,500. In order to obtain practical physical properties as a polyurethane with respect to 100 parts by weight of the low molecular weight prepolymer, it is necessary to use 10 to 20 parts by weight of the diisocyanate. When such a large amount of diisocyanate is added to a low-molecular-weight polyester melted at 150 ° C. or higher, gelation occurs and a melt-moldable resin cannot be obtained.

Also, as in the case of polyurethane rubber,
A method of converting a hydroxyl group into an isocyanate group by adding a diisocyanate and further increasing the number average molecular weight with a glycol may be considered, but the amount of the diisocyanate used may be reduced as described above. 10 parts by weight or more is required per part by weight. At this time, if a heavy metal-based catalyst is used for the synthesis of the polyester, the reactivity of the isocyanate group is remarkably promoted, resulting in poor storage stability, crosslinking reaction, and branch formation, so that the polyester prepolymer is synthesized without a catalyst. As a result, the number average molecular weight is limited to about 2,500 at the highest.

In the polyester prepolymer for obtaining the aliphatic polyester used in the present invention, the terminal group obtained by reacting the glycol with an aliphatic polybasic acid or its anhydride is substantially a hydroxyl group. A saturated aliphatic polyester having a relatively high molecular weight of 5,000 or more, preferably 10,000 or more, and a melting point of 50 ° C. or more.

When the number average molecular weight is less than 5,000, for example, about 2,500, good physical properties can be obtained even when a small amount of 0.1 to 5 parts by weight per 100 parts by weight of the prepolymer is used. Unable to get polyester. Polyester prepolymers having a number average molecular weight of 5,000 or more have a hydroxyl value of 30 or less, and use of a small amount of a coupling agent does not cause gelation during the reaction even under severe conditions such as a molten state. Polyester can be synthesized.

Examples of the glycols used for the synthesis of the prepolymer include ethylene glycol, butanediol 1,4, hexanediol 1,6, decamethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol and the like. . Ethylene oxide can also be used. These glycols may be used in combination.

The aliphatic dicarboxylic acids or derivatives thereof which form aliphatic polyesters by reacting with glycols include succinic acid, adipic acid, suberic acid, sebacic acid, dodecanoic acid, succinic anhydride, adipic anhydride and their derivatives. There are lower alcohol diesters such as dimethyl ester and the like, which are commercially available and can be used in the present invention. Polybasic acids or derivatives thereof may be used in combination. These compounds may be preliminarily converted into low molecular esters to be polymerized by a glycol removal reaction.

These glycols and dicarboxylic acids are mainly composed of aliphatic compounds, but may be used in combination with small amounts of other components, for example, aromatic compounds. However, if other components are introduced, the biodegradability deteriorates. Therefore, the content is 20% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less.

[0015] The polyester prepolymer for aliphatic polyester used in the present invention has a terminal group substantially a hydroxyl group. For this purpose, glycols and polybasic acids (or acid anhydrides thereof) used in the synthesis reaction are used. The proportion used requires the use of some excess of glycols.

In order to synthesize a polyester prepolymer having a relatively high molecular weight, it is preferable to use a deglycol-reaction catalyst in the deglycolization reaction following the esterification in order to ensure the polymerization.

Examples of the deglycol-reaction catalyst include titanium compounds such as acetoacetoyl-type titanium chelate compounds and organic alkoxytitanium compounds.
These titanium compounds can be used in combination. Examples of these include diacetacetoxyoxytitanium ("Nersem Titanium" manufactured by Nippon Chemical Industry Co., Ltd.), tetraethoxytitanium, tetrapropoxytitanium, tetrabutoxytitanium and the like. The use ratio of the titanium compound is 0.001 to 100 parts by weight of the polyester prepolymer.
To 1 part by weight, preferably 0.01 to 0.1 part by weight. The titanium compound may be added from the beginning of the esterification, or may be added immediately before the deglycolization reaction.

As a result, the polyester prepolymer usually has an acid average molecular weight of 5,000 or more, preferably 20,000.
A material having a melting point of 0 or more and a melting point of 60 ° C. or more can be easily obtained, and it is more preferable that the material has crystallinity.

In order to obtain the aliphatic polyester of the present invention, the number average molecular weight is further 5,000 or more, preferably 1 or more.
Coupling agents are used to further increase the number average molecular weight on polyester prepolymers where the terminal groups at or above 000 are substantially hydroxyl groups.

Examples of the coupling agent include diisocyanates, oxazolines, diepoxy compounds, acid anhydrides, etc., and diisocyanates are particularly preferred. In the case of an oxazoline or diepoxy compound, it is necessary to react a hydroxyl group with an acid anhydride or the like and convert the terminal to a carboxyl group before using a coupling agent.

The diisocyanate is not particularly limited,
For example, there are the following types. 2,4-tolylene diisocyanate, 2,4-tolylene diisocyanate and 2,
Mixture with 6-tolylene diisocyanate, diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, particularly hexa Methylene diisocyanate is preferred from the viewpoint of the hue of the formed resin, the reactivity at the time of adding the polyester, and the like.

The amount of the coupling agent to be added is 0.1 to 5 parts by weight, preferably 0.5 to 3 parts by weight based on 100 parts by weight of the polyester prepolymer. If the amount is less than 0.1 part by weight, the coupling reaction is insufficient. If the amount exceeds 5 parts by weight, gelation occurs.

The addition is desirably carried out under conditions in which the polyester prepolymer is in a uniform molten state and can be easily stirred. It can be added to a solid polyester prepolymer and melted and mixed through an extruder, but it is added to an aliphatic polyester production apparatus or to a molten polyester prepolymer (for example, in a kneader). It is practical.

The aliphatic polyester resin has a temperature of 190.
The melt viscosity at 100 ° C. and a shear rate of 100 (sec ⁻¹ ) is preferably 3.5 × 10 ^{3 to} 4.0 × 10 ⁴ poise. If the melt shear viscosity is less than 3.5 × 10 ³ poise, the melt viscosity is too low, so that surging and uneven resin temperature are apt to occur during extrusion molding, and the extrusion stability is lacking. However, there is a disadvantage that the thickness of the laminated film becomes large and the thickness of the resulting laminated film becomes large. On the other hand, if the melt shear viscosity exceeds 4 × 10 ⁴ poise, the melt viscosity is too high, so that the load on the motor during extrusion molding increases and productivity decreases, and it is difficult to reduce the thickness of the molten film during lamination molding. is there. Preferably, the melt shear viscosity is 4 × 10 ^{3 to} 1.6 × 10 ⁴ poise. More preferably, the melt shear viscosity is in the range of 5 × 10 ^{3 to} 1.2 × 10 ⁴ poise.

The melting point of the aliphatic polyester used in the present invention is preferably from 60 to 85 ° C. When the melting point is less than 60 ° C., when the paper cups are stacked and packed for distribution, or when the paper cups are mounted on a cup holder of a vending machine, the surface is easily damaged and the paper cups adhere to each other, which is not preferable. When the melting point exceeds 85 ° C., when the formed paper cup is buried in soil and decomposed by microorganisms, the rate of biodegradation is undesirably slow. Preferably, the melting point is 65-80 ° C.

The aliphatic polyester resin has a number average molecular weight of 10,000 or more and a urethane bond of 0.03 or more.
特 徴 3.0% by weight. Number average molecular weight is 1
A substrate having a polyester layer having a strength as described above is obtained only when the molecular weight is at least 000, and can be used for various applications. If it is less than 10,000, heat resistance also decreases,
It also becomes brittle in terms of strength and is unsuitable as a substrate having practical strength.

In the present invention, a base material for a paper container can be produced by laminating the aliphatic polyester resin produced by the above method on base paper by the T-die method. The temperature of the extruded resin at this time is
290 ° C. If the resin temperature is lower than 150 ° C., the melt viscosity is too high, so that the motor load at the time of extrusion molding is increased and the productivity is reduced, and it is difficult to reduce the thickness of the molten film at the time of lamination molding. On the other hand, when the resin temperature is 29
When the temperature exceeds 0 ° C., the resin composition deteriorates, surging or the like occurs, and extrusion stability is lacking, or neck-in of the molten film at the time of laminating is performed. The width of the molten film at the exit of the T-die and the width of the laminated film laminated on the substrate are large and unstable, making it difficult to form the laminate. is there. Preferably, the resin temperature is 160 to 270 ° C, more preferably, the resin temperature is 170 to 250 ° C.

Extrusion lamination molding in which an aliphatic polyester resin is extruded and laminated on base paper can be carried out using a general screw type extruder and a laminator.
A molten resin film made of an aliphatic polyester resin is extruded on one or both sides of the base paper supplied at 0 to 200 m / min, and is bonded to the base paper by pressure bonding between a cooling roll and a pressing roll, and the molten resin film is formed on the surface of the cooling roll. After contact cooling and solidifying, a roll is wound up or a continuous cutting machine is passed on a cut plate. The cooling roll used in the present invention may have any surface finish such as a mat, a semi-matte, and a mirror. This is necessary for use in a vending machine because of the removal property of each piece) and the roll separation at the time of laminating is preferable. When the content is a sparkling beverage such as a carbonated beverage, mirror finishing is preferable because it has a smaller contact area with the content and has an antifoaming effect. Therefore, a combination of semi or mirror finish on the inner surface and mat or mirror finish on the outer surface is preferred.

Further, in the present invention, an ozone gas or the like is blown onto the bonding surface of the molten film with the paperboard in a space between the molten film extruded from the T-die and the so-called air gap, that is, between the air gaps, so as to adhere to the paperboard. A method of strengthening the properties and adhesion may be adopted.

In order to enhance the adhesiveness of the aliphatic polyester composition with paperboard, a tackifier such as a terpene resin or an adhesive such as an ionomer, an ethylene-acrylate copolymer, or an acid-modified polyolefin is used. Resins may be added within a range that does not impair the performance of the paper laminate of the present invention. Further, the paperboard may be subjected to a pretreatment such as an anchor coat treatment, a corona treatment, and a frame treatment to strengthen adhesion and adhesion to the laminate film.

When using the polyester resin of the present invention, it is needless to say that a lubricant, a wax, a coloring agent, a filler and the like can be used in combination, if necessary. Particularly, in addition to the conventional lubricant, a lubricant such as VITON was very effective in improving the surface smoothness. Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.

[0032]

【Example】

(Example 1) In a 100-liter autoclave equipped with a stirrer, a fractionating condenser, and a thermometer, 27.2 kg of hexanediol 1.6 and 46 kg of dodecaneic acid were charged, and esterified in a nitrogen stream at 200 to 205 ° C. After the acid value was adjusted to 7.3, 150 g of tetraethoxygermanium [manufactured by Nippon Chemical Industry Co., Ltd.] was used as a glycol removal catalyst.
and finally 0.4 Torr at 210-215 ° C.
The deglycol reaction was performed for 18 hours under reduced pressure to obtain an aliphatic polyester prepolymer (X) having a number average molecular weight of 16,100 (a white wax-like polymer at room temperature). Melting point was 83 ° C.

When the temperature was lowered to 200 ° C. and 800 gr of isophorone diisocyanate was added, the viscosity increased rapidly.

After stirring at the same temperature for 10 minutes, an aliphatic polyester (D) containing a small amount of urethane bonds was obtained. This polyester (D) has a molecular weight of about 22,000 and a temperature of 19
The melt-shear viscosity at a shear rate of 100 sec ^-1 at 0 ° C. was 7 × 10 ³ poise, a slightly waxy white wax at room temperature, and the melting point was 83 ° C.

Then, the polyester resin (D) was fed to an extruder having a screw diameter of 50 mmφ and L / D = 28 to a width of 320 mm.
resin temperature (manufactured by Rika Kogyo Co., Ltd .: using a contact type thermometer, resin extruded from the T-die at a predetermined screw rotation speed in the T-die) using a straight manifold T-die having a lip gap of 0.8 mm. Base paper (280 g / m ² ) extruded at a temperature of 220 ° C. and subjected to a corona discharge treatment (processing amount 30 w min / m ² ) supplied at a speed of 130 m / min.
² ) Extrusion lamination with a thickness of 20 μm on top to produce a paper container base material. At the time of lamination molding, the molten film was stable and excellent in film formation stability, and there was little smoke and the working environment was good. The evaluation of the obtained base material is shown in Table 1.

The laminated base material was cut into a rectangle of 10 cm × 20 cm and attached to a square box made of stainless steel with a polyethylene net sandwiching the laminated base paper. This was buried in soil having a depth of 10 cm, and the biodegradability was evaluated. The place is the garden of Showa Denko KK Kawasaki Resin Laboratory (Kawasaki-ku, Kawasaki City). When dug out three months later, it was found that the polyester thin film was more decomposed than the paper fiber and had become ragged.

Example 2 In the same manner as in Example 1, an aliphatic polyester resin (D) was extrusion-laminated at a resin temperature of 190 ° C. and a thickness of 20 μm on base paper supplied at a speed of 80 m / min. Wood was obtained. At the time of lamination molding, the molten film was stable and excellent in lamination moldability. The obtained laminate substrate had good adhesion and water resistance. The evaluation of the substrate is shown in Table 1.

Comparative Example 1 In the same manner as in Example 1, the aliphatic polyester composition (D) was extrusion-laminated at a resin temperature of 140 ° C. and a thickness of 60 μm onto base paper supplied at a speed of 50 m / min. Wood was obtained. Since the melt viscosity was too high, it was difficult to reduce the thickness of the polyester resin layer. The lower limit was 60 μm, and no further reduction was possible. Nevertheless, at the time of lamination molding, the molten film was stable and the lamination moldability was good. The evaluation of the obtained base material is shown in Table 1.

(Comparative Example 2) When an attempt was made to laminate the aliphatic polyester resin (D) at a resin temperature of 300 ° C., the molten film of the composition was so surging that a laminated film having a constant width and a constant thickness could be obtained. Did not. Table 1 shows other evaluations.

(Example 3) Stirrer, fractionating condenser,
In a 100 liter autoclave equipped with a thermometer and a gas inlet tube, 11.5 kg of ethylene glycol, 1,4
-4 kg of butanediol, 46 kg of dodecanoic acid,
Charge 2 gr of tetrabroxytitanium, 200-205
After esterification in a nitrogen stream at a temperature of 5.4 ° C. to an acid value of 5.4,
Perform a glycol removal reaction at 215 to 220 ° C. for 10 hours,
Finally, the pressure was reduced to 0.6 Torr, and the number average molecular weight was 1
6,400 aliphatic polyester prepolymers (XI)
was gotten. Upon cooling to room temperature, it became a slightly brownish wax and had a melting point of about 65 ° C.

The obtained polyester prepolymer (X
I) The whole amount is heated to 200 to 202 ° C. to be melted, and 400 g of xylylene diisocyanate is stirred with stirring.
Was added. The viscosity increased rapidly but no gelling occurred. After stirring for 20 minutes, the resulting aliphatic polyester (E) containing urethane bonds has a molecular weight of 28,000, a melt shear viscosity at a temperature of 190 ° C. and a shear rate of 100 seconds ⁻¹ of 1.3 × 10 ⁴ poise, Yellowish brown wax, melting point was about 69 ° C.

In the same manner as in Example 1, this aliphatic polyester resin (E) was extruded onto a base paper fed at a speed of 130 m / min at a resin temperature of 240 ° C. and a thickness of 20 μm to obtain a base material for a paper container. . At the time of lamination molding, the film formation stability was good, and the adhesion of the obtained laminate substrate was also good.
The evaluation of the obtained base material is shown in Table 1.

Example 4 An aliphatic polyester resin (E) was extruded onto a base paper fed at a speed of 130 m / min at a resin temperature of 180 ° C. and a thickness of 20 μm. I got The laminate moldability was good, and the adhesion of the obtained laminate substrate was also good.
The evaluation of the obtained base material is shown in Table 1.

(Comparative Example 3) Many paper cups of an ice coffee vending machine coated with paraffin wax having a melting point of 50 ° C were obtained and subjected to the following evaluation.

When the paper laminate used for the paper cup was scratched by the edge of the spoon, the paraffin wax was easily peeled off and the adhesion was poor. Further, after the paper cup was strongly bent, iced coffee with ice was put therein, left for one hour, and then lifted up.

Further, when the biodegradability of the paper laminate was evaluated, the paraffin wax of the paper laminate had almost no change in appearance and no biodegradability. The evaluation is shown in Table 1.

<< Experimental Results >> 1) Laminating Formability: The neck-in stability of the molten film and the uneven thickness stability of the laminate film were evaluated. ：: The neck-in of the molten film during lamination molding was 80 mm
In the following, there is almost no variation, and the thickness deviation of the laminated film is within 10% except for the ears. ×: The neck-in of the molten film during lamination molding was 80 mm.
When the variation is 10 mm or more on one ear and the thickness deviation of the laminated film exceeds 10% excluding the ear part.

2) Adhesion: The resin surface of the paper laminate was scratched with the edge of a spoon made of polypropylene, and the state of peeling of the resin layer of the paper laminate was observed. It is preferable that the evaluation is ○. ：: A state in which there is no blistering or peeling of the resin layer, adhesion is good, and durability can be expected. ×: A state in which there was blistering or peeling of the resin layer, there was a problem in adhesion, and there was an anxiety in durability.

3) Water resistance: A paper cup for a vending machine is manufactured from the paper laminate having water resistance, and vertical streaks are firmly attached by hand to four places on the side of the paper cup. One hour after the iced coffee was poured, the state of the paper cup was observed. It is preferable that the evaluation is ○. ： １: When the paper cup is lifted after one hour, the fold is firm and easily lifted without any swelling. ×: When the paper cup was lifted after one hour, the fold was soft and was likely to be deformed.

4) Biodegradability; 10 cm × 2
The paper laminate of 0 cm was sandwiched between stainless steel molds provided with a polyethylene net at the window, buried in soil of 10 cm in depth, dug out three months later, and evaluated for its biodegradability.
It is preferable that the evaluation is ○. ：: When the aliphatic polyester composition of the paper laminate is more decomposed than paper, and the surface of the composition is perforated with perforations. ×: when the decomposition of the paper has progressed from the aliphatic polyester composition of the paper laminate and the aliphatic polyester composition is still firm.

[0051]

[Table 1]

[0052]

According to the present invention, the melt viscosity is 3.5 × 10 ^3-
4.0 × 10 ⁴ poise, melting point relates paper containers for substrates for cold food products obtained by laminating a 50 to 85 ° C. of the aliphatic polyester resin in the base paper, the base material of biodegradation in soil And has a configuration that is extremely easy to dispose without causing environmental pollution.

Further, the aliphatic polyester resin is excellent in laminating processability, and the obtained base material has good adhesion and good water resistance, and furthermore, there is no cracking or peeling of the laminated layer which is a water repellent layer. It can be advantageously used as a cold drink or as a base material for disposable containers.

Continued on the front page (72) Koji Furuichi 3-2 Chidori-cho, Kawasaki-ku, Kawasaki-ku, Kanagawa Prefecture Showa Denko KK Kawasaki Resin Laboratory (72) Inventor Eiichiro Takiyama 4-12-4 Nishi-Kamakura, Kamakura-shi, Kanagawa Prefecture (56 References JP-A-2-222421 (JP, A) JP-A-4-146952 (JP, A) JP-A-4-146953 (JP, A) JP-A-3-109830 (JP, U) U.S. Pat. (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (2)

(57) [Claims] 1. A prepolymer having a number average molecular weight of 5,000 or more.
After preparing the polymer, 100 parts by weight of the prepolymer
0.1-5 parts by weight of the coupling agent is reacted,
A main constituent unit is a glycol having a melt viscosity of 3.5 × 10 ^{3 to} 4.0 × 10 ⁴ poise at 90 ° C. and a shear rate of 100 (sec ⁻¹ ) and a melting point of 60 to 85 ° C. and an aliphatic dicarboxylic acid. A base material for a paper container for cold drinks, wherein the aliphatic polyester resin is laminated on a base paper. 2. The base material for a paper container for a cold food or drink according to claim 1, wherein the aliphatic polyester resin is laminated on base paper at a resin temperature of 150 to 290 ° C.