JPS62131060A - Heat-shrinkable polyamide film - Google Patents

Abstract

PURPOSE:To provide the titled film having a high heat shrinkage factor at a relatively low temp. and gas barrier properties, by molding a mixture of two specified polyamides into a film and biaxially orienting the film. CONSTITUTION:5-30% (by weight; the same applies hereinbelow) polyamide (A) obtd. by polymerizing 100-85% polyamide-forming component (a) consisting of an aliph. diamine (e.g., hexamethylenediamine) and isophthalic acid and/or terephthalic acid with 0-15% polyamide forming component (b) consisting of a lactam (e.g., caprolactam) or an aliph. diamine and an aliph. dicarboxylic acid (e.g., adipic acid) is mixed with a polyamide (B) obtd. by polymerizing 70-99% aliph. polyamide forming component with 30-1% polyamide forming component consisting of at least one aliph. diamine and at least one arom. dicarboxylic acid (c). the mixture is molded into a film by the T-die method, etc. and an unoriented film is oriented at 120 deg.C or below at a draw rate of 10,000%/sec or above and a draw ratio of 2.0X2.0 or above to obtain the titled film having a shrinkage factor of 25% or above in hot water at 75 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a shrinkable polyamide film which has a high 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 for meat packaging such as ham and daily goods, but these have low gas barrier properties and are subject to quality degradation due to oxidation etc. It was unsuitable for packaging products that change. Polyvinyl chloride
Although the +7dene copolymer is a material that has both oxygen barrier properties and shrinkage properties, it is not fully satisfactory due to its strength and problems when incinerating used films. t-
Various shrink films based on polyamides such as nylon have been proposed, but their shrinkability, especially 7j'C1fl
The subsequent hot water shrinkage at relatively low temperatures 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 appropriate as such.

[Purpose of the invention]

The inventor Tera conducted repeated studies on various polyamides in order to develop a heat-shrinkable film that has a high hot water shrinkage rate of 1% at relatively low temperatures of around 7J℃ and also has good gas barrier properties. We have now discovered a polyamide film that meets this purpose.

[Structure of the invention]

That is, the present invention comprises 100-r!% by weight of a polyamide-forming component consisting of an aliphatic diamino and isophthalic acid and/or terephthalic acid, and 0% by weight of a polyamide-forming component consisting of a lactam or an aliphatic diamine and an aliphatic dicarboxylic acid.
-/! polyamide (A) formed by polymerizing i% by weight, an aliphatic polyamide-forming component of 70 to 7% by weight, a polyamide-forming component consisting of at least one aliphatic diamine, and one or more aromatic dicarboxylic acids; A coaxially stretched polyamide film made by mixing polyamide (B) formed by polymerizing and! L This relates to a heat-shrinkable polyamide film characterized by a hot water shrinkage rate of 2j% or more at 7j°C.

Since 9E, the hot water shrinkage rate at 7J℃ of polyamide or copolyamide whose main component is caprolactam is 2J
% or less, and had poor adhesion to the contents during shrinkage, whereas the shrinkable polyamide film of the present invention showed a hot water shrinkage rate of 23% or more at 75°C, and this drawback has been improved. be.

The present invention will be explained in detail below.

Constituting the heat-shrinkable polyamide film of the present invention (Al
The polyamide is a film-formable polyamide whose main component is aromatic polyamide, and the aromatic polyamide-forming component ta+ and the aliphatic polyamide-forming component +1) are (a)
/(b)=/ 0070~! ! It is a copolyamide copolymerized at a ratio of //j. (aJ is composed of aliphatic diamine and inphthalic acid and/or terephthalic acid, and aliphatic diamines include straight chain aliphatic diamines such as ethylene diamine, tetramethylene diamicom, hexamethylene diamine, oztamethylene diamine, decamethylene diamine, etc.) It contains diamine and its methylated, ethylated, halogenated, etc. derivatives, and its /a to Ja1 or more can be used during polymerization.The composition of inophthalic acid and terephthalic acid is terephthalic acid!O weight % or more, the melting point of polyamide (Al) becomes 300°C or higher, and polyamide fB
), it is preferable that the amount is less than 0% by weight of terephthalic acid, but it is preferably 0 to 35% by weight of terephthalic acid. Lactams that can be used in (t)l include caprolactam, lauryllactam, and the like. The aliphatic diamines that can be used in the present invention include the same ones as in (a),
Aliphatic dicarboxylic acids include succinic acid, glutaric acid, adipic acid, pimeli/fl11 speric acid, azelaic acid, sebacic acid, and their methylation and ethylation.

It contains derivatives such as -・Rogge/chemicals, etc., and 7/44J or two or more types can be used during polymerization.

As for the polymerization composition, if the component (b) exceeds iz vehicle ms, the shrinkage rate and gas barrier properties will decrease (a)
As for the combined composition of (t)1O, it is necessary to make BL 0 to 71% by weight, but from the viewpoint of thermal stability during polymerization and fluidity of the polymer, it is preferably 70% by weight or less.

Next, the heat-shrinkable polyamide film of the present invention is constructed (
The polyamide B) is a film-formable polyamide mainly composed of aliphatic polyamide, and the aliphatic polyamide-forming component (C1) and the aromatic polyamide-forming component (d) are
It is a copolyamide copolymerized at a ratio of l/+a+=70/30 to tata/l.

The aliphatic diamines, lactams, and aliphatic dicarboxylic acids that can be used in the present invention each include (specific examples of Al), but at the time of polymerization, two or more of them can be used. Aromatic dicarboxylic acids that can be used to form (d) include isophthalic acid, terephthalic acid, or these acids with alkyl groups, halogen groups, etc. having a carbon number of 1 to 2 in the ring. Substituted compounds can be mentioned, and in the case of % polymerization, /W1 to 12 or more can be used.

In polyamide (Bl), if the aromatic polyamide-forming component dl exceeds 30% by weight, the pellets will be severely fused, so (d) is preferably set to 7 to 30% by weight.

Next, the mixing ratio of polyamide fAl and polyamide (B) is (
Al! 7 if less than 30% by weight or more than 30% by weight
The hot water shrinkage rate at 1℃t, p: is 25% or more.
Hard to get. Therefore, the mixing ratio of +Al component is (A) and FB+
For the total amount of! ~30% by weight is preferred, but more preferably lO ~ λ! Weight%.

The copolyamide used in the present invention is manufactured by the following methods. That is, a nylon salt or aqueous solution consisting of a lactam and/or diamine and dicarboxylic acid is formed. This was placed in an autoclave and, if necessary, a so-called monofunctional compound such as a monocarboxylic acid or a monoamine was added to control the degree of polymerization, and then the mixture was heated at a temperature of 210°C or higher at normal pressure or after initial pressure, while gradually releasing the pressure. In addition to the history of condensation, polycondensation can also be carried out by a solution polymerization method or an interfacial method.

The method of mixing polyamide fA) and polyamide (Bl) is usually by thoroughly mixing the respective chips, or by melt-kneading them one or more times in a bath using an extruder, etc., but the methods are not particularly limited to these. When polymerizing polyamide fAl and/or polyamide TBI, thermal stabilizers such as acid esters, surfactants,
Antifoaming agents, antioxidants, anti-blocking agents, pigments, etc. can be added. Similarly, the above-mentioned additives can be added when mixing polyamide fAl and polyamide (Bl) or when forming a film.

The film is usually plasticized by the inflation method or the τ-die method at a molding temperature higher than the melting point of either polyamide (Al or polyamide (Bl), and the film extruded from the die is usually rapidly cooled to a temperature of 10°C or less. An unstretched film is obtained.

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 laterally stretched in a tenter. For simultaneous biaxial stretching, use the tenter method or tubular method.
Methods such as legal methods are used. The unstretched film may be subjected to rlA humidity conditioning before the stretching step, or may be dried.

If the stretching temperature exceeds 120°C, workability is poor, so it is necessary to keep the stretching temperature below 100°C, and more preferably 20 to 60°C.

If the stretching speed is less than 70,000%/(8), the shrinkage rate decreases, so it is necessary to be at least 10,000%/(8), and more preferably at least 20,000%/(8).

The stretching ratio is 2.0×2. 2. If the value is less than θ, the shrinkage rate decreases. OX, 0 or more is required, but preferably ! ×2. j or more.

Heat setting of the film after biaxial stretching causes a decrease in yield due to strain relaxation, crystal growth, etc., so careful control is required. / Heat set at 20°C for 0-110 seconds, preferably 30-10 seconds, and then cooled to 60°C or less.

The heat-shrinkable polyamide film of the present invention thus obtained has a hot water shrinkage rate of 25% or more at 73°C in both the longitudinal stretching direction, v4#, and stretching direction of the film, compared with conventional nylon-6, nylon-y -6/Aj copolymer film shows better shrinkage properties than metaxylylene/
It is a nylon-based heat shrinkable film that does not have the disadvantage that the contents deform when it shrinks like adipamide films, and has achieved unprecedented suitability as a shrinkable film.
A highly developed polyamide film is provided, and its practical value is great.

The heat-shrinkable polyamide film of the present invention may be coated with polyolefin (holyethylene/,
It is clear that polypropylene, ethylene-vinyl acetate copolymers, saponified products thereof, etc.), modified polyolefins/or polyesters, etc. can be multilayered as long as the shrinkability is not adversely affected.

〔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 using the following methods.

(IJ ηrel It was determined from the ratio of the number of seconds of falling of a solution of 7% by weight of a polymer dissolved in sulfuric acid with a concentration of t% by Ostwald viscometer at 2 J° C. divided by the number of seconds of falling of the solvent.

f21Tg (glass transition temperature) It was determined by differential scanning calorimetry.

(3) Mark a square αXjcIIL on the hot water shrinkage stretched film, and
After the film was soaked in a water bath controlled at .degree. C. for several minutes, the film was taken out and the hot water shrinkage rate was determined by determining the vertical and horizontal dimensional difference .DELTA.L of the initially marked square.

Example 1 (a) (^) Production of component copolymerized polyamide Distilled water jJk
g to hexamethidi/diamine aqueous solution (J' Owt%)
IJ, 9 kg, (S7 talic acid?, rkl s terephthal RG Hiroshi, ri kp ft), stirred and dissolved uniformly, further added rn acid j3?, then charged into an autoclave.
12. While keeping the pressure at F/cat, water is distilled out at a temperature of 1 degree (Owt%) of nylon salt, and then the pressure is increased to /3 kg/- without heating, water is further distilled out, and the internal temperature is 210 When the temperature reached ℃, the internal pressure was reduced to 9℃, and finally, the polymerization was carried out under reduced pressure of 700 torr for 1 hour to form chips.The polymer thus obtained had a ηre of 120.2, Tg=/J7℃. Met.

(B) (B) Production of component copolymerized polyamide Distilled water
Add caprolactam μjkP to g, r kp
After keeping the pressure at 1/cdl, water was further evaporated, and when the internal temperature reached 23-0℃, the internal pressure was slowly released and the final step was to perform vacuum polymerization at a reduced pressure of 700 torr for ≠θ minutes. Made into chips. The polymer obtained in this way is ηrel = J, /, 2, Tg = rj
It was ℃.

The copolyamide obtained in (b) above was mixed in the form of chips using a V-type filter/puller, then extruded through a T-die at a barrel temperature of λtzo°C and a die temperature of 210°C, and bound into a film at 50°C. The film was wound up using a cast roll in which warm water was flowed to obtain a 200 μm film that was substantially unstretched.

This unstretched film was heated to 4 jt17 by tenter method.
ct-7c oi%TD (!: also2J
'Stretch it twice and heat set it for 30 seconds at IOO℃ and then roll it up 2! A film of μ was obtained.

Table 1 shows the hot water shrinkage rate of this film.

Example 2 Except for mixing 10% by weight of the (A) component copolyamide obtained in (a) of Example 1 and 20% by weight of the (B) component copolyamide obtained in (b). Table 1 shows the hot water shrinkage rates of the films obtained in the same manner as in Example 3.

Example 3 The procedure of Example 1( C)
Table 1 shows the hot water shrinkage rates of the films obtained in the same manner as above.

Example μ In Example 1 (c), ♂! The hot water shrinkage rate of the film obtained in the same manner as in Example/, except that the film was stretched at .degree. C., is shown as fi/.

Comparative Example 1 When the Bl component copolyamide obtained in (b) of Example 1 was formed into a film in the same manner as (c) of Example 1, the hot water shrinkage rate of this film is shown in Table 1. .

Comparative Example λ 70 parts of the fBl component copolyamide obtained in (b) of Example 1 and nylon 6 (Mitsubishi Kasei ■!R10200A)
30 parts were mixed into a film in the same manner as in (c) of Example 1, and the hot water shrinkage rate of this film is shown in Table 1.

Comparative Example 3 The above nylon-6 was prepared at a barrel temperature of 260°C and a die temperature of λ.
The film was extruded from a T-die at 0.degree. C. and wound from a cast roll through which warm water at 10.degree.

This unstretched film was subjected to a tenter method to obtain λ, J'X2. in both MD and TD. Stretched 3 times at 700℃
After heat fixing for 0 seconds, winding λ! I got a film of μ. Table 1 shows the hot water shrinkage rate of this film.

Example! (A) Production of component (A) copolymerized polyamide Distilled water j J
kg of hexamethylene diamine (t Owt%)
Add 19J kg of terephthalic acid and 19J kg of terephthalic acid, stir evenly, and then add caprolactam 2. Added acetic acid, and added acetic acid to the fourth. The subsequent operations were carried out in the same manner as in Example 1 (a) to obtain a copolyamide.

ηrel of this polymer = ,2,07, Tq
= 120°C.

(B) (Production Example 1 of Bl component copolymerized polyamide
In (a), caglolactam≠2. A copolymerized polyamide was obtained in the same manner as in Example 1 (a) except that jky hequibumethylene diamine (r Owt% aqueous solution) was used. This polymer had ηrel=j, //1Tg=I 7°C.

The copolyamide rrH portion obtained in (b) above was formed into a mixed film in the same manner as in (c) of Example 1. Table 1 shows the hot water shrinkage rate of this film.

【Effect of the invention〕

As shown in Table 1, the shrinkable polyamide film obtained by the present invention has a higher hot water shrinkage rate at relatively low temperatures than conventional polyamide films, and has great utility value.

Sender: Mitsubishi Chemical Industries, Ltd. Representative: Patent Attorney Hase - 1 other person

Claims (1)

[Claims] (1) Polyamide forming component 100 to 85 consisting of aliphatic diamine and isophthalic acid and/or terephthalic acid
% by weight, a polyamide (A) obtained by polymerizing 0 to 15% by weight of a polyamide forming component consisting of a lactam or aliphatic diamine and an aliphatic dicarboxylic acid, and 70 to 99% by weight of an aliphatic polyamide forming component and one or more A polyamide (B) obtained by polymerizing an aliphatic diamine of
1.) A heat-shrinkable polyamide film, which is a biaxially stretched polyamide film prepared by mixing the following: