JPS6241261A - Heat-shrinkable polyamide film - Google Patents

Abstract

PURPOSE:To provide the titled film having excellent gas barrier properties and low shrinkage in hot water under low-temperature conditions and suitable for use in packaging foods, daily necessaries, etc., by biaxially orienting a compsn. composed of an arom. polyamide and an aliph. polyamide. CONSTITUTION:A monomer mixture of 85-100wt% arom. polyamide forming component composed of terephthalic acid and/or isophthalic acid and an aliph. diamine (e.g. hexamethylenediamine) and 15-0wt% aliph. polyamide forming component composed of a lactam component or an aliph. dicarboxylic acid and an aliph. diamine is (co)polymerized to obtain an arom. polyamide (A) 10-40wt% component A and 90-60wt% aliph. polyamide (e.g. nylon-6 or 66) are melt-kneaded and the mixture is molded into a film by inflation or T-die extrusion. The resulting unoriented film is stretched at 120 deg.C or below and at a stretching rate of 10,000%/sec or above by means of a casting roll and then tentered by a tenter to thereby biaxially orient it at a draw ratio of 2.0X2.0 or above. The film is then set by heat.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention particularly relates to a force-shrinkable polyamide film which has a large hot water shrinkage rate at relatively low temperatures and also has good gas barrier properties.

[Conventional technology]

Conventionally, polyolefins, polystyrene, polyvinyl chloride, etc. are known as heat-shrinkable films that have been widely used in meat packaging such as ham and household goods, etc. However, these films have low gas barrier properties, so their quality deteriorates due to oxidation etc. Polyvinylidene chloride copolymer is a material that has both oxygen barrier properties and shrinkability, but it has problems with strength and when incinerating used film. It is not completely satisfactory.6-
Various shrink films based on polyamides such as nylon have been proposed, but what about their shrinkability? The hot water shrinkability at relatively low temperatures around j'C was not fully satisfactory. Furthermore, polyamide whose main component is a condensate of metaxylylene diamine and aliphatic dicarboxylic acid has been proposed as a shrink film, but it has the disadvantage that the shrinkage stress is large and the Young's modulus is too high, causing the contents to deform. It was not suitable as a film.

In order to develop a heat-shrinkable film that has both a high shrinkage rate in hot water and good gas barrier properties, we have repeatedly investigated polyamides for fences, and as a result, we have found a polyamide film that meets these objectives.

[Structure of the invention]

That is, the gist of the present invention is a biaxially stretched film of a polyamide resin composition comprising an aromatic polyamide (A) and an aliphatic polyamide (B), the film comprising an aromatic polyamide (AJ
is an aromatic polyamide forming component consisting of terephthalate/I/[and/or isophthalic acid and aliphatic diamine't, Hg
5 - A heat-shrinkable polyamide film which is obtained by polymerizing a polyamide containing 5-weight or more, and has a hot water shrinkage rate of 20% or more at 75°C. .

The present invention will be explained in detail below.

The hot water shrinkage rate at 75°C of conventional polyamides or copolyamides containing caprolactam as the main component is SO
% or less, resulting in poor adhesion to the contents during shrinkage, whereas the shrinkable polyamide film of the present invention exhibits a hot water shrinkage ratio of 1θ or more at 3°C, and this drawback has been improved. It is something that

The aromatic polyamide (A) constituting the heat-shrinkable polyamide film of the present invention is a film-formable polyamide containing an aromatic group, and is an aromatic polyamide-forming component consisting of terephthalic acid and/or isophthalic acid and an aliphatic diamine. It is obtained by polymerizing monomers containing 7a-3, i-1 or more. It may be a homopolymer in which the formation rate is 100% by weight or more, but the aliphatic polyamide forming component Y/ consisting of the formation rate of 3% by weight or more and a lactam component or an aliphatic dicarboxylic acid and an aliphatic diamine may be used. -! l'X-! It may also be a copolymer obtained by polymerizing a heptamer mixture containing 1% or less. Aliphatic diamines include ethylene diamine, tetramethylene diamine, hexamethylene diamine, octamethylene diamidated, ethylated or halogenated derivatives! In the polymerization, two or more types of /ffi or χ can be used. In the case of copolymers, the lactams for summer use include caprolactam, lauryllactam, and the like. Similarly, aliphatic dicarboxylic acids used in copolymerization include succinic acid, glutaric acid, adipic acid, pimelic acid, superric acid, azelaic acid, sebacic acid, and those in which the methylene group of these compounds is methylated or ethyl. It contains a compound or a halogenated derivative, and one or more of them can be used during polymerization.

In addition, aliphatic polyamides (BJ include nylon-6, nylon-6,6, nylon-6,10 and nylon-4/
l, A copolymer, nylon-A/A, /θ together! Associations etc? I can give an example.

Heat-shrinkable polyamide film of the present invention! Configure (A)
The aromatic polyamide component is polymerized under conditions in which the aromatic polyamide-forming component consisting of isotutaric acid and/or terephthalic acid and aliphatic diamine is 3% by weight or more, but the lactam component or aliphatic dicarboxylic acid and aliphatic If the content of the aliphatic polyamide-forming component consisting of diamine exceeds 13% by weight, the shrinkage rate and gas barrier properties will decrease, so the copolymerization component must be proportionate in weight from O to L. In terms of stability and fluidity of the polymer, the copolymerization component is less than or equal to 1, and the aromatic polyamide component is 93%.
It is preferable that it is at least % by weight.

Next, aromatic polyamide (A) and aliphatic polyamide (B)
The mixing ratio is (AJ is io weight'!L-chi~!Io weight%
, CB) is preferably in the range of 90% to 60% by weight. (A) is less than 70% by weight, or 4IO% by weight
If it exceeds 10%, the hot water shrinkage rate at 75°C will be less than 10%, so a heat-shrinkable film that meets the purpose of the present invention will not be obtained. Therefore, the mixing ratio of component (A) will be /0-40% by weight.
However, more preferably 13 to 5xfJ
k%.

Aromatic group-containing polyamide component (A
) is usually produced by the so-called melt polymerization method by adding a lactam if necessary to a nylon salt or its aqueous solution consisting of diamine and dicarboxylic acid, but depending on the composition of isophthalic acid and terephthalic acid/acid, a solution method may be used. Alternatively, it is produced by interfacial polymerization.

The composition of isophthalic acid and terephthalic acid is 0 compared to terephthalic acid.
If the melting point of the polyamide component (AJ is yoo
℃ or more, making it difficult to mix with the aliphatic polyamide, so it is necessary that the content be less than 300% by weight, and more preferably terephthalic acid O to 33% by weight.

The method of mixing aromatic polyamide (AJ) and aliphatic polyamide (B) is usually by thoroughly mixing the respective chips or melt-kneading them seven or more times using an extruder, etc., but is not particularly limited to these methods. It's not something you can do.

If necessary, when polymerizing aromatic polyamide (A) 'a', polymerization terminal terminators such as monocarboxylic compounds and monoamines, thermal stabilizers such as phosphoric acid esters, surfactants, antifoaming agents, and antioxidants are added. Agents, anti-blocking agents, pigments, etc. can be added.

Similarly, aromatic polyamide Ck) and aliphatic polyamide CB
) 'h: The above-mentioned additives can be added during mixing or film forming.

The film is usually formed by an inflation method or a T-die method at a molding temperature higher than the melting point of either polyamide (A) or polyamide (B).
The film extruded from the die is usually rapidly cooled to a temperature of 80° C. or lower to obtain an unstretched film.

To obtain a sequentially biaxially stretched film, a method is used in which an unstretched film extruded from a T-die is longitudinally stretched using a casting roll, and then transversely stretched in a tenter. In the case of simultaneous biaxial stretching, a tenter method, a tubular method, etc. are used. The unstretched film may be subjected to humidity conditioning or drying before proceeding to the stretching step.

When the stretching temperature exceeds /20C%, workability deteriorates and it is necessary to keep the stretching temperature below 120C, but 10 to 60C is more preferable.

A stretching speed of 10,000%/sec or more is required since shrinkage groups decrease when the stretching speed is less than 0.000%/7 sec, and more preferably 0.000%/sec or more.

If the stretching ratio is lower than O, OX, the shrinkage rate will decrease, so λ, Ox of 2.0 or more is required, but preferably CO, sx,! That's all.

Heat setting of the film after biaxial stretching requires careful control as it leads to a decrease in shrinkage rate due to strain relaxation, crystal growth, etc.
cooled down.

The heat-shrinkable polyamide film of the present invention obtained in this way has a temperature of Aθ°C or higher of hot water nylon-A/1.
It is a nylon-based heat-shrinkable film that exhibits better shrinkability than 6-copolymer films, and does not have the drawbacks of deforming the contents during shrinkage, which is the case with films such as metaxylylene adipamide. A polyamide film is provided that is suitable as a shrink film, and has great practical value.

The heat-shrinkable polyamide film of the present invention may be coated with polyolefin (such as HolJ ethylene, polypropylene, ethylene-vinyl acetate copolymer and saponified products thereof), modified polyolefin, polyester, etc. on at least one side of the film, if necessary, to adversely affect shrinkability. It can be multi-layered as long as it does not cause any damage.

〔Example〕

EXAMPLES The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited to these Examples.

The measurement items in the examples were carried out by the following methods.

(1) ηred Determined from the ratio of the number of seconds for a solution containing 77% by weight of polymer dissolved in sulfurized solution having a concentration of 1% to fall by an Ostwald viscometer at 23°C divided by the number of seconds for the solvent to fall.

(2) Tg (glass transition temperature) It was determined by differential scanning calorimetry.

(3) Hot water yield rate: 3α× for stretched film! Mark the square of rcrIL, 7
After soaking this film in a water bath controlled at 5°C for Y minutes, remove the film and mark the vertical direction of the positive sign shape that was originally marked.
The lateral dimensional difference ΔLY was determined, and the hot water yield rate was determined by the following formula: Shrinkage light (%) = ΔL/yoX 110 0 (() (σ).

Example 1 Distilled water 33
Add 9, isophthalic acid, zayu, terephthalic acid, and 9 to fk%n/3.9, stir and dissolve uniformly, and then add acetic acid! 3
After adding fi'lj, put it into an autoclave. While keeping the pressure at h kg/di, water is distilled out until the concentration of nylon salt becomes 0.1 mass, and then / 3
After increasing the pressure to kg/crA, water is further distilled out and when the internal temperature reaches 3θ℃, the internal pressure is slowly removed and what happens at the end? The resulting product was subjected to vacuum polymerization at a reduced pressure of 0.00 Torr for 1 hour to form chips. The polymer thus obtained had a 1re12,j, Tg/u 7 °C.

This polymer, nylon-110T for 20% weight
After mixing Li% in chip form using a V-type tumbler,
The film was extruded through a T-die at a barrel temperature of 2 AOC and a die temperature of 210° C., and wound up from a cast roll in which hot water at 0° C. was flowed to obtain a substantially unstretched film of −〇θμ.

This unstretched film was stretched 4x in both MD and TD at t and sr by a tenter method to 100'
After heat fixing in CVC for 30 seconds, wind up and
A film of 5μ was obtained. Hot water shrinkage IKy of this film
a' Table ■ shows.

Example 1 The hot water shrinkage rate of the film obtained in the same manner as in Example 1 except that the polymer 10'' x amount obtained in the same manner as in Example 1 was mixed with nylon-6 by weight is shown. Shown in I.

Example 3 30% by weight of the polymer obtained in the same manner as in Example 1 and 70 sq. of nylon! ! Table I shows the hot water shrinkage rates of the films obtained in the same manner as in Example 1, except that the amounts were mixed.

Example G Polymer obtained in the same manner as Example/110 weight! to%
Table 1 shows the hot water shrinkage rates of the films obtained in the same manner as in Example 1 except that nylon-t, y, 5t, and o were mixed in weight percent.

Example! g! of the film obtained in Example 1. Table I shows the hot water shrinkage rate of the film obtained by stretching at r°C.

Example 6 Hexamethylene diamine aqueous solution C10 in 3 kg of distilled water
heavy i-cloudy]i11. okg, isophthalic acid 10, Akl
, terephthalic acid t, j kfl, ε-caprolactam 1. Dissolve tkg of water by stirring uniformly, and then add 6<< of acetic acid.
, p'v was added and then charged into an autoclave. Hereinafter, melt polycondensation was carried out using the same one-component recipe as in Example 1.

The polymer thus obtained is ηre1=co, /,
Tg was 120°C.

A stretched film was obtained in the same manner as in Example 1 by mixing 20% by weight of this polymer with nylon-6 and tit% by weight of gO. Table 1 shows the hot water shrinkage rate of this film.

Comparative example 1 Nylon-6t barrel temperature 0℃, die temperature 210
The film was extruded from a T-die at 30°C and wound up from a cast roll through which warm water at 30°C was flowed to obtain a 200μ film with substantially no stretching.

This unstretched film was stretched by a tenter method in both MD and TD to a length of 1 g x λ, heat-set at 100° C. for 30 seconds, and then wound to obtain a film with a thickness of 23 μm.

The hot water shrinkage properties of this film are shown in Table I.

Table I * MD: 1 Stretching direction TD: Transverse stretching direction [Effects of the invention] As described above, the polyamide film of the present invention has high heat shrinkability even at relatively low temperatures, and also has the disadvantage that the contents deform when shrinking. It is useful for food packaging and daily miscellaneous goods.

Claims (1)

[Claims] (1) Aromatic polyamide (A) and aliphatic polyamide (B)
), wherein the aromatic polyamide (A) contains 85% by weight or more of an aromatic polyamide-forming component consisting of terephthalic acid and/or isophthalic acid and an aliphatic diamine. A heat-shrinkable polyamide film obtained by polymerizing a monomer that is characterized in that the film has a hot water shrinkage rate of 20% or more at 75°C.