JP2012066506A - Laminated material for paper container and paper container obtained by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated material for a paper container, which comprises a paper layer and a PET resin layer and in which the low-temperature heat sealability is ensured by modifying an inexpensive PET resin and the extrusion properties when being extruded/layered onto the paper layer are improved by heightening the viscosity or tension in melting.SOLUTION: A chain extender is added to the PET resin having 0.55-0.7 dL/g intrinsic viscosity, to charge the PET resin into an extruder having two or more vent holes. In a state where the PET resin is heated/melted, the PET resin is sucked/deaerated through the vent holes in high vacuum of -750 mmHg or lower. Thereafter, the PET resin is extruded onto the paper layer to laminate the PET resin layer thereon. Immediately after the PET resin layer is laminated, a PET resin layer surface is cooled quickly by a cooling roller. The chrystalline portion of the PET resin layer is expressed by formulae: the crystalline portion (%)=100×(a melting calorie per mol-cooling crystallization calorie per mol)/{a melting calorie per mol of a perfect crystal PET (26.9 KJ)}; and a noncrystalline portion (%)=100-the crystalline portion; wherein the crystalline portion is <15% and the noncrystalline portion is ≥85%.

Description

  The present invention relates to a laminated material for paper containers and a paper container made from the same, and more specifically, when a resin layer serving as an inner surface laminated on paper is made as a paper container as a PET resin layer having good aroma retention. The present invention relates to a paper container to which heat sealability is imparted or heat resistance is imparted by applying post-boxing heat to the paper container.

  Currently, there are many paper containers for beverages such as vegetable juice, milk, yogurt, Japanese tea and coffee, alcoholic beverages such as sake and shochu, liquid seasonings such as noodle soup and pure oil, cup ramen, cups such as ice cream, etc. It is used. For these paper containers, a laminate material for paper containers in which a polyolefin resin layer, particularly a polyethylene resin layer is laminated on the inner surface is used in order to provide water resistance and to make a box easily by heat sealing. Yes. However, the polyethylene resin has a problem that it absorbs a flavor component typified by d-limonene and loses its flavor, and cannot be used for beverages that place importance on flavor.

  By the way, PET resin is used as the most common resin that does not adsorb flavor components and is low in cost, and is used as a PET bottle in fruit juice drinks. However, since the PET resin is a crystalline resin, it cannot be used as it is because it has poor low-temperature heat-sealability that is necessary for making paper containers.

  Therefore, polyethylene is blended with polyester composed of terephthalic acid, isophthalic acid and ethylene glycol (see Patent Document 1), or amorphous to low crystalline modified polyethylene terephthalate having a glass transition point of 40 ° C. or higher is used (patent). Reference 2), 50% by mole or more of the dicarboxylic acid component is terephthalic acid, and the diol component is 40 to 90% by mole of ethylene glycol and 10 to 60% by mole of an ethylene oxide adduct of bisphenols. There has been proposed a technique of using a polyester composed of 97 to 50 parts by weight and 3 to 50 parts by weight of an epoxy group-containing ethylene copolymer (see Patent Document 3).

JP-A-2-277635 Japanese Patent Laid-Open No. 9-77051 Japanese Patent Laid-Open No. 11-49940

  However, the technique proposed in Patent Document 1 has a problem that there is no low-temperature heat sealability (about 130 ° C. inside or outside) comparable to that of a polyethylene resin. There was a risk of occurring depending on the blend amount. In addition, the techniques proposed in Patent Documents 2 and 3 are not normally produced PET resins, and both of them need to be newly synthesized, resulting in high costs.

  The present invention has been made in order to solve the above problems, and is a paper container in which a PET resin layer laminated so as to ensure a low-temperature heat-seal property similar to that of a polyethylene resin by modifying an inexpensive PET resin. Another object of the present invention is to provide a laminated material for use, and in addition, to increase the viscosity and tension at the time of melting and to improve the extrusion characteristics when extrusion lamination is performed on a paper layer.

  It is another object of the present invention to provide a paper container that can ensure heat resistance of 200 ° C. or higher that can withstand microwave ovens.

  The inventors of the present invention diligently studied to solve the above-mentioned problems, and when laminating a PET resin layer on a paper material to produce a laminated material for a paper container composed of a paper layer and a PET resin layer, the paper material is laminated. If the crystal part of the PET resin layer is made less than 15% and the amorphous part is made 85% or more by quenching the surface of the PET resin layer immediately after with a cooling roll, even if an inexpensive PET resin is used, it looks like a polyethylene resin. The inventors have found that low temperature heat sealability can be obtained, and have completed the present invention.

  Also, by adding a chain extender to a PET resin having an intrinsic viscosity of 0.55 to 0.7 dl / g and heating and melting it in an extruder, the PET molecular chains are combined to give a high molecular weight of a three-dimensional structure. It is found that the extrusion characteristics are improved by this, and the PET resin is put into an extruder having two or more vent holes, and the vent holes are heated and melted in the PET resin. From the above, it was found that moisture can be removed by suction and deaeration under a high vacuum of −750 mmHg or more, and the present invention has been completed.

  Moreover, even if it is a paper container boxed by heat sealing, if the crystal part of the PET resin layer is raised to 35% or more by maintaining the optimal crystallization temperature of PET resin at 130 ° C. to 220 ° C., The inventors have found that heat resistance of 200 ° C. or higher can be imparted, and have completed the present invention.

  That is, the laminated material for paper containers according to claim 1 adds a chain extender to PET resin having an intrinsic viscosity of 0.55 to 0.7 dl / g, and puts it into an extruder having two or more vent holes, After the PET resin is heated and melted, it is sucked and degassed from the vent hole under a high vacuum of −750 mmHg or more, and then extruded onto the paper layer to laminate a PET resin layer. In the PET resin layer, the crystal part represented by the following formula is less than 15%, and the amorphous part is 85% or more.

  The laminated material for paper containers according to claim 2 is characterized in that the chain extender has two or more polyfunctional epoxy groups.

  The laminated material for paper containers according to claim 3 is characterized in that the addition amount of the chain extender is 0.2 to 2.0 parts by weight with respect to 100 parts by weight of the PET resin.

  A paper container according to a fourth aspect is characterized in that the paper container laminate is used, and the PET resin layer surface of the paper container laminate is used as an inner surface and bonded by heat sealing.

  The paper container according to claim 5 is provided with heat resistance by maintaining the temperature at 130 ° C. to 220 ° C. after producing the paper container and increasing the crystal portion represented by the following formula of the PET resin layer to 35% or more. It is configured as a feature.

  In the laminated material for paper containers according to claim 1, the molten PET resin is extruded onto the paper layer, the PET resin layer is laminated, the PET resin layer surface immediately after the lamination is quenched with a cooling roll, and the following formula of the PET resin layer: Since the amorphous portion shown in FIG. 5 is 85% or more, heat sealing can be performed satisfactorily.

すなわち、ヒートシールは一般的なＰＥ樹脂やＰＰ樹脂の場合はその結晶が溶ける温度（ＰＥ＝約１１０℃、ＰＰ＝約１６０℃）以上にヒートシール温度を上げて結晶を完全に溶かして溶融混合させ、同じ樹脂同志であれば完全に一体化して剥れなくなる。しかし、ＰＥＴ樹脂の場合は、その結晶を溶かす融点は約２６０℃であり、その温度まで上げてヒートシールすることは、高温すぎてあまり現実的でない。

That is, in the case of general PE resin and PP resin, the heat seal is melted and mixed by completely melting the crystal by raising the heat seal temperature to a temperature above which the crystal melts (PE = about 110 ° C., PP = about 160 ° C.). If they are the same resin, they will be completely integrated and will not peel off. However, in the case of PET resin, the melting point for dissolving the crystals is about 260 ° C., and it is not practical to raise the temperature and heat seal it because it is too hot.

  On the other hand, a general PET resin is a polymerization reaction of terephthalic acid and ethylene glycol, but this glycol component was completely polymerized with terephthalic acid at 65 mol% of ethylene glycol and 35 mol% of cyclohexanedimethanol. It becomes crystalline (see FIG. 3) and is sold as a PET-based resin that can be heat-sealed at 130 ° C. (“Easter PETG6763” Nagase Sangyo Co., Ltd.)

  Therefore, even if a general PET resin has a large amount of amorphous parts, even if the crystalline part is not melted, it will not be peeled off by soft mixing of the amorphous part, but the crystal acts as a foreign matter as a hindrance to heat sealing and heats well. There was a case that could not be sealed. Therefore, the present inventors diligently investigated the relationship between the amorphous part and the crystal part in heat sealing, and when the amorphous part is 85% or more and the crystal part is less than 15%, heat sealing is performed extremely well. It has been found that can be.

  In addition, since a chain extender is added to a relatively low molecular weight PET resin having an intrinsic viscosity of 0.55 to 0.7 dl / g and heated and melted, the low molecular weight PET molecular chains are combined to form a three-dimensional structure. This is a high molecular weight PET resin. Therefore, the viscosity and tension of the molten PET resin are increased, and the extrusion characteristics at the time of extrusion lamination to the paper layer are improved.

  Furthermore, using an extruder having two or more vent holes, the PET resin is heated and melted, and is sucked and degassed from the vent holes under a high vacuum of −750 mmHg or higher, so that the contained moisture can be removed by suction. . Therefore, it is not necessary to dry the PET resin in advance.

In the laminated material for paper containers according to claim 2, since it has two or more polyfunctional epoxy groups as a chain extender, it binds low molecular weight PET molecular chains having a linear structure and has a high molecular weight of 3 It can be easily performed to obtain a PET resin having a dimensional structure.

In the laminated material for paper containers according to claim 3, the addition amount of the chain extender is 0.2 to 2.0 parts by weight with respect to 100 parts by weight of the PET resin. By setting it as such a range, it can modify | reform as a PET resin of a high molecular weight three-dimensional structure by required optimal amount.

In the paper container according to the fourth aspect, the laminate for paper containers is used, and the PET resin layer surface of the laminate for paper containers is used as an inner surface and bonded by heat sealing. Water resistance, high quality that does not cause flavor adsorption of beverages, and high sealing and sealing can ensure high safety and hygiene without foreign substances and bacteria.

In the paper container according to claim 5, after the paper container is manufactured, the temperature is maintained at 130 to 220 ° C., and the crystal portion represented by the following formula is increased to 35% or more to impart heat resistance. Can also be used for microwave ovens.

Schematic diagram of the cylinder part of an extruder having two or more vent holes used for producing the laminated material for paper containers of the present invention Diagram showing the crystallization rate (insoluble catalyst) of PET A diagram showing that the structural formula and crystallization rate of PETG are substantially zero.

  In the laminated material for paper containers according to the present invention, a PET resin layer is laminated on a paper layer, and it is sufficient that the PET resin has an intrinsic viscosity of 0.55 to 0.7 dl / g. Therefore, it is not necessary to use a high-quality PET resin, and it is possible to use a low-priced PET resin for fibers and the like, so that a laminated material for paper containers can be provided at a low cost.

  Furthermore, since moisture is removed in the heating / melting step in the extruder, the moisture content of the PET resin does not need to be 50 ppm or less, which is usually required when extruding the PET resin, and the equilibrium moisture content in the air. It may be 0.3 to 0.5%, and it is not necessary to provide a preliminary drying step.

  Such a PET resin is put into an extruder with a chain extender added. By using a chain extender, a polymer having a three-dimensional network structure is formed when linking low molecular weight PET molecular chains, and viscosity and melt tension are increased to improve extrusion suitability. Examples of the chain extender include glycidyl acrylate, glycidyl methacrylate, styrene-methyl (meth) acrylate-glycidyl methacrylate, epoxidized soybean oil, and the like, and have at least two polyfunctional epoxy groups. It is preferable. The chain extender having two or more polyfunctional epoxy groups is sold by BASF Japan Ltd., Toa Gosei Co., Ltd., etc., for example, BASF Japan Ltd. “JONCRYL”, Toa Gosei Co., Ltd. ) “ARUFON”.

  The addition amount of the chain extender is preferably 0.2 to 2.0 parts by weight with respect to 100 parts by weight of the PET resin, and the addition amount is appropriately increased or decreased according to the performance of the chain extender.

  The chain extender is added by spraying liquid paraffin or castor oil on PET resin pellets with 0.05 to 0.20 wt% Henschel mixer, etc., then adding the chain extender powder, and mixing and adhering with Henschel mixer. The chain extender can be uniformly added by such an addition method. When the addition amount of the chain extender is small and easily nonuniform, it is preferable to prepare and add a master batch. The master batch is prepared by adding 10 to 50 parts by weight of a chain extender to 100 parts by weight of PET resin, kneading with an extruder, and pelletizing. If this master batch pellet is added to a predetermined amount of PET resin pellet and mixed and stirred with a blender or the like, it can be added uniformly.

  Moreover, you may add the catalyst of a metal salt to PET resin as needed. Examples of metal salts include stearates and laurates of alkali metals and alkaline earth metals, but the most common and preferred is calcium stearate. The addition amount is 0.05 to 1.5 parts by weight with respect to 100 parts by weight of the PET resin, and a master batch is prepared with the PET resin and added.

  The PET resin added with the chain extender as described above and, if necessary, a metal salt catalyst, is put into an extruder having two or more vent holes, and is heated and melted to increase the vacuum to -750 mmHg or more from the vent holes. After suction and degassing with, it is extrusion laminated on the paper layer.

FIG. 1 shows a schematic diagram of a cylinder portion of an extruder having two or more vent holes. In FIG. 1, reference numeral 1 denotes a cylinder. A screw 2 is provided inside the cylinder 1, and a first vent hole 3 and a second vent hole 4 are formed from the base end side (PET resin charging side). In the screw 2, the compression / compression unit 21 and the seal unit 22 are alternately arranged. In the seal unit 22, the groove width of the screw is narrowed and the space between which is filled with molten PET resin, and the compression / compression unit 21 seals the pressure difference between the high back pressure of 100 to 200 kg / cm ² and the vent hole 3 and the high vacuum of −750 mmHg at 4 parts, and the resin is pushed only by the rotation of the screw 2 so that the vent hole 3 4 prevents the molten resin from blowing up.

  The vent holes 3 and 4 are connected to an oil rotary vacuum pump (not shown) via a condenser (condenser) (not shown), and the condenser maintains the degree of vacuum and the oil rotary vacuum. This is to maintain the oil quality of the pump. Without a condenser, for example, if a PET resin with a water content of 3,000 ppm is operated at a discharge rate of 500 kg / hr, 500,000 g × 0.3 / 100 = 1,500 g / hr of water vapor is generated and high. The vacuum cannot be maintained, and the oil in the oil rotary vacuum pump is also altered by water.

In the extruder as described above, in order to melt and extrude the PET resin, the PET resin is put into the cylinder 1, the extrusion temperature is 280 ° C. inside / outside, the back pressure is 100 to 200 kg / cm ² , the vent holes 3 and 4 to −750 mmHg Extrusion is performed under suction and deaeration under the above high vacuum.

  First, the charged PET resin is kneaded with the chain extender added by heating and melting in the first zone. It is considered that the molten PET resin is depolymerized by hydrolysis and thermal decomposition with water and heat, and low molecular PET chains, ethylene glycol, and acetaldehyde are generated. However, since the chain extender is added from the beginning and kneaded, it is thought that polymerization reactions such as three-dimensional molecular weight increase and ethylene glycol and acetaldehyde capture have started to occur by linking low molecular weight PET chains. It is done. Ie epoxy group

は開裂して、カルボキシル基（−ＣＯＯＨ）、アルデヒド基（−ＣＨＯ）、水酸基（−ＯＨ）等の官能基と結び付き、ＰＥＴ分子鎖を３次元の網目構造の高分子にするとともに、解重合で生じたエチレングリコール、エチレングリコールから発生するアセトアルデヒドをも高分子の一部として捕捉する。また、含有している水分は、２８０℃における飽和水蒸気圧は６５ｋｇ／ｃｍ^２であるので、背圧１００ｋｇ／ｃｍ^２以上では液体の状態である。

Is cleaved and combined with a functional group such as a carboxyl group (—COOH), an aldehyde group (—CHO), a hydroxyl group (—OH), etc., and the PET molecular chain is converted into a polymer having a three-dimensional network structure. The generated ethylene glycol and acetaldehyde generated from ethylene glycol are also captured as part of the polymer. Moreover, since the saturated water vapor pressure at 280 ° C. is 65 kg / cm ² , the contained water is in a liquid state at a back pressure of 100 kg / cm ² or more.

  And when the molten PET resin containing ethylene glycol, acetaldehyde, and water comes to the 1st vent hole 3, since it is under a high vacuum of -750 mmHg or more, ethylene glycol (boiling point 198 ° C.), acetaldehyde (boiling point 20) ° C.) and water (boiling point 100 ° C.) become gas and are sucked and degassed from the first vent hole 3. Further, ethylene glycol, acetaldehyde and water that have not been completely sucked and degassed from the first vent hole 3 are sucked and degassed by the second vent hole 4.

  In the second zone, it is considered that a part of the depolymerization has occurred, but most of the polymerization reaction by the chain extender is considered to have occurred.

  In the third zone, almost only the polymerization reaction by the chain extender occurs, and a high molecular weight PET resin having a three-dimensional structure is extruded and laminated on the paper layer. At this time, the air gap from the T-die is as short as possible, and it is preferable that the two rolls sandwiched between the rolls are cooling rolls. It is necessary to cool quickly. That is, as shown in FIG. 2, the crystallization rate of PET is fast in the range of about 130 to 220 ° C. Therefore, in order to suppress crystallization as much as possible, it is necessary to shorten the residence time in this temperature range. Yes, it is possible to quickly pass through this temperature zone by cooling rapidly. As a result, the amorphous part of the PET resin can be 85% or more.

  As the cooling roll, at least the PET resin layer side roll is preferably a metal roll through which cooling water is passed.

The paper material used for the paper layer on which the PET resin is extrusion laminated is not particularly limited, although cup base paper, gable top and brick type paper containers are used for cups. The basis weight of the paper material varies depending on the size and shape of the paper container, usually 50 to 500 g / ^{m 2,} for example in the cups 100 to 400 g ^/ m 2, in 1l gable-top container of 280 g / ^{m 2} and out, 1. In an 8 l gable top container, it is 370 g / m ² inside and outside.

  In order to form a paper container using the laminated material for paper containers as described above, the PET resin layer is heat-sealed as the inner surface of the paper container. Although there are some box making machines that directly heat the heat-sealed surface with flames or hot air, generally there are many box making machines that heat and heat seal with a hot plate. In that case, since heating is performed by a hot plate from the paper layer side which is a heat insulating material, it is important from the viewpoint of productivity that the heat seal temperature is a heat seal temperature as low as polyethylene.

  A paper container is made by punching a paper container laminate into a blank of the paper container to be made, a gable top type, a brick type, and cups, and the contents are vegetable juice, There are beverages such as milk, yogurt, Japanese tea and coffee, alcoholic beverages such as sake and shochu, liquid seasonings such as noodle soup and pure oil, cup ramen, ice cream and the like.

  Beverages and cups that do not require heat resistance can be used as they are after boxing, but for microwave ovens it is necessary to further impart heat resistance. In order to impart heat resistance, after forming in a paper container, the temperature is maintained at 130 to 220 ° C. in a thermostatic bath, and the crystal portion represented by the following formula of the PET resin layer is set to 35% or more, whereby The above heat resistance can be provided.

図２はＰＥＴの結晶化速度（不溶性触媒）を表わしたもので横軸に結晶化温度、縦軸に半結晶化時間を採ったものである。この図より１３０〜２２０℃が最適な結晶化温度であることが判る。すなわち１３０℃未満では分子の自由度が小さくなり、また２２０℃以上では結晶化のドライビングフォースが小さくなるので結晶化速度が遅くなるものである。

FIG. 2 shows the crystallization rate (insoluble catalyst) of PET, with the horizontal axis representing the crystallization temperature and the vertical axis representing the half crystallization time. From this figure, it can be seen that 130 to 220 ° C. is the optimum crystallization temperature. That is, when the temperature is lower than 130 ° C., the degree of freedom of the molecule becomes small, and when the temperature is higher than 220 ° C., the driving force for crystallization becomes small, so that the crystallization speed becomes slow.

Unitika Co., Ltd. PET resin “MA-2101M” (inherent viscosity: 0.62 dl / g, water content: 2,900 ppm) 100 parts and BASF Japan Co., Ltd. chain extender “AdR4368” contained 30% by weight 1.5 parts of the master batch of PET was mixed and stirred with a Henschel mixer. This mixed resin is put into a Hitachi Zosen Co., Ltd. co-rotating twin-screw extruder “HMT100” (L / D = 38, discharge amount: 650 kg / hr, 2 vent holes), and the extrusion temperature is 280 ° C. while sucking to degas in a high vacuum of -755MmHg, extrusion laminated to a paper layer 250 g / ^{m 2,} to prepare a paper layer (250g ^/ m 2) ^/ PET resin layer paper containers laminate material (25 [mu] m) .

  The cooling roll was a cooling roll through which chiller water at 25 ° C. passed through the PET resin layer, and the vent hole was connected to an oil rotary vacuum pump via a condenser. The air gap is 12 cm and 50 m / min. And 130 m / min. Laminated at the processing speed.

<Behavior of moisture content>
130 m / min. The screw and vacuum suction during the continuous extrusion were temporarily stopped at the processing speed, the resin at the first and second vent hole positions of the extruder was sampled, and the moisture content was measured. The moisture measurement was performed using a plastic moisture vaporizer ADP-351 (Kyoto Electronics Co., Ltd.) and a Karl Fischer moisture meter MKC-210 (Kyoto Electronics Co., Ltd.). The results are shown in Table 1.

  The moisture content in the undried PET resin is 10 ppm or less at the position of the first vent hole, and clears 50 ppm or less, which is usually essential when the PET resin is extruded. It becomes 0 ppm at the position of the 2nd vent hole, and it turns out that it is not necessary to dry beforehand by suction and deaeration from a vent hole.

<Residual acetaldehyde>
130 m / min. The PET resin layer is peeled from the paper container laminate laminated at a processing speed of 1, and cut into a size of 1 cm x 2 cm, and a large number of cut pieces corresponding to a surface area of 250 cm ² on the front and back are provided with 500 ml of slitting stoppers Into a glass Erlenmeyer flask.

Next, air in the Erlenmeyer flask was replaced with N ₂ gas at 40 ° C. in a room at 40 ° C. (N ₂ gas 2 ml / surface area 1 cm ² ), then sealed with a stopper and left at 40 ° C. for 24 hours. The gas phase in the Erlenmeyer flask treated in this manner was judged by the odor paneler for the presence or absence of off-flavor, and the acetaldehyde in the gas phase was gas chromatograph GC-6A type manufactured by Shimadzu Corporation with an FID detector. It was measured. The results are shown in Tables 2 and 3.

  No odor was felt in the panel odor test, and no acetaldehyde was detected by gas chromatography, so it was confirmed that there was no residual acetaldehyde.

<Evaluation of flavor adsorption>
130 m / min. The PET resin layer is peeled off from the paper container laminate laminated at a processing speed of 5 cm × 10 cm, and 5 sheets (total 250 cm ² ) of 100% d-limonene, which is the main flavor component of citrus fruits It was immersed in a liquid and left in a constant temperature bath at 23 ° C.

  After 1 day and 7 days, the PET resin layer was taken out, the surface d-limonene solution was quickly wiped off with a filter paper, the weight was measured, and the weight increase due to adsorption of d-limonene into the PET resin layer was determined. At the same time, an LDPE resin film having a thickness of 30 μm was cut into the same size and measured in the same manner. The results are shown in Table 4.

  It can be seen that the increase in the weight of the PET resin layer is much smaller than that due to the adsorption of the LDPE resin film and there is no flavor adsorption.

<Ratio of amorphous and crystalline parts due to differences in processing speed>
The PET resin layer was peeled from the paper container laminate (paper layer / PET resin layer), its dissolution behavior was measured with a Seiko Electronic DSC220 differential scanning calorimeter, and the proportion of the crystal part was measured based on the following formula. The amorphous part was calculated by amorphous part (%) = 100−crystal part (%).

結果を表５に示す。

The results are shown in Table 5.

  As can be seen from Table 5, the faster the processing speed, the faster the temperature range of 130 ° C. to 220 ° C., which is the optimum crystallization temperature of PET, passes, so there are many amorphous parts.

<Ratio of amorphous part that can be heat sealed>
Machining speed 130 m / min. The laminate for paper containers (paper layer / PET resin layer) laminated in (1) was left in a constant temperature bath at 170 ° C. and heat-treated to produce samples having different amorphous portions. The amorphous part was calculated by DSC measurement as described above. The results are shown in Table 6.

  Next, the PET resin layer was peeled off from the paper container laminate, and the PET resin layers were joined together and heat sealed. Heat sealing was performed according to JISZ-1707 with a pressure of 0.2 Mpa and a sealing time of 1 second. Table 7 shows the results of the seal strength.

  As can be seen from Table 7, the ratio of the amorphous part that can be heat-sealed in the same manner as PE is 85% as the boundary ratio.

<Comparison with paper layer / PE resin layer laminate>
In general, a paper container laminate composed of a paper layer (250 g / m ² ) / PE resin layer (30 μm) used as a paper container laminate, and a processing speed of 130 m / min. The laminated material produced in (1) was sealed by applying a hot plate from the paper layer side as it was. The sealing conditions were 0.3 Mpa and the sealing time was 2 seconds. The results are shown in Table 8.

  As can be seen from Table 8, it is bonded from a lower temperature than a paper container laminate composed of a normal paper layer / PE resin layer.

<Production of paper container>
Machining speed 130 m / min. A 1.0 liter gable-top type paper container was produced using the laminated material laminated in step 1 using a gable-top box-making machine. The results were able to be produced under almost the same conditions as those for a paper container laminate using a normal PE resin layer.

<Preparation of heat-resistant paper container>
Machining speed 130 m / min. A short cup-shaped paper container having an upper diameter of 15.5 cmΦ, a lower diameter of 14.5Φ, and a height of 4 cm was prepared using a cup-type box making machine. This container was placed in a 200 ° C. thermostat and subjected to heat treatment for 8 minutes to produce a heat-resistant paper container. The PET resin layer of this heat-resistant paper container was peeled off, and the ratio of the crystal part was measured based on the following formula by DSC measurement as described above.

  As a result, the ratio of the crystal part was 41.8%. Moreover, the PET resin layer on the inner surface was whitened by the crystal of the PET resin layer.

  Next, a commercial frozen gratin was placed in this container, and cooking was performed at 250 ° C. for 15 minutes in an oven. Gratin was well cooked. After the contents were taken out and washed, the appearance of the PET resin layer on the inner surface of the container was observed, but there was no appearance of the PET resin being melted and there was no change in the appearance before and after cooking.

1 Cylinder 2 Screw 3 First vent hole 4 Second vent hole

Claims (5)

A chain extender is added to a PET resin having an intrinsic viscosity of 0.55 to 0.7 dl / g, and the mixture is put into an extruder having two or more vent holes, and the PET resin is heated and melted from the vent holes. After sucking and degassing under a high vacuum of 750 mmHg or more, an extruded PET resin layer is laminated on the paper layer, and immediately after the lamination, the surface of the PET resin layer is quenched with a cooling roll, and the crystal represented by the following formula of the PET resin layer A laminated material for paper containers, wherein the portion is less than 15% and the amorphous portion is 85% or more.

The laminate for a paper container according to claim 1, wherein the chain extender has two or more polyfunctional epoxy groups. The laminated material for paper containers according to claim 1 or 2, wherein the addition amount of the chain extender is 0.2 to 2.0 parts by weight with respect to 100 parts by weight of the PET resin. A paper container comprising the paper container laminate according to claim 1, wherein the PET resin layer surface of the paper container laminate is an inner surface and bonded by heat sealing. After producing the paper container according to claim 4, the temperature is maintained at 130 to 220 ° C., and the crystal portion represented by the following formula of the PET resin layer is increased to 35% or more to impart heat resistance. Paper container.

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