JPS6024813B2 - resin composition - Google Patents

Description

Detailed Description of the Invention The present invention is made of a saponified ethylene monoacetate pinyl copolymer and a specific aliphatic copolymer polyamide, which has excellent stretchability, gas barrier properties, heat resistance, DK resistance, oil resistance, impact resistance, etc. In particular, it relates to a resin composition suitable for continuous molding of packaging materials.

Saponified ethylene-vinyl acetate copolymer (hereinafter referred to as EVOH)
) has extremely low oxygen gas permeability, excellent oil resistance, and transparent molded products can be easily obtained by ordinary melt forming processing methods, so it is especially suitable for films, sheets, etc.
It is useful as a packaging material for tubes, plastic containers, etc. However, on the other hand, EVOH is hydrophilic, so it has high moisture permeability and lacks hot water resistance, is hard and brittle, has an impact strength of 4.5 mm, and has extremely low stretchability, so its uses are expanding. is restricted.
As one of the means to improve the above-mentioned drawbacks of conventional EVOH,
Method of mixing polyamide with VOH (Hakama Kosho 44-24
No. 277, Japanese Patent Publication No. 48-22833, Japanese Patent Publication No. 121347-198) have been proposed, and this method maintains the gas barrier properties, good transparency, and oil resistance that are the characteristics of EVOH. It is known that impact strength is improved.

In fact, when a composition of EVOH and polycaproamide is applied to a film for packaging materials, it has the following characteristics. {1) EVOH has extremely poor stretchability and can only be stretched in one touch at a low magnification under limited conditions, but when polycaproamide is blended with EVOH, the stretchability is dramatically improved.
Biaxial stretching is also possible. [21 The gas barrier properties of an unstretched film blended with polycaproamide, which has inferior gas barrier properties compared to EVOH, are lower than those of EVOH alone, but the blended composition is highly oriented and crystallized by stretching and subsequent heat setting. Therefore, the deterioration in gas barrier properties not only becomes virtually negligible, but also improves in some cases.

■ The effects of orientation and crystallization caused by stretching and heat setting also improve properties such as hot water resistance, dimensional stability, and mechanical strength.
A stretched film made of a blended composition of VOH and polycaproamide has better hot water resistance than expected from a stretched film made of EVOH alone, suppresses dimensional changes due to water absorption, and has anisotropy of mechanical properties of 4. Sashi,.

As described above, compositions made of EVOH and polycaproamide exhibit many desirable properties as packaging materials and molded articles with high commercial value can be obtained, but they actually have serious drawbacks. This is because when EVOH and volicaproamide are mixed in a molten state, a chemical reaction occurs between the two, resulting in an increase in the viscosity of the mixed composition, resulting in intense coloring and gelation. That is, due to this disadvantageous phenomenon, it is difficult to continuously mold a composition made of EVOH and polycaproamide, and it is not possible to apply a continuous manufacturing process to practical products such as films, sheets, and tubes. For example, for an EVOH with an ethylene content of 3% by weight, a degree of kelization of 99%, and an intrinsic viscosity (measured in 15% by weight of water-containing phenol at a temperature of 300 mm; the same applies hereinafter) of 0.13 mm, the relative viscosity (
One volume of polymer was dissolved in 100% concentrated sulfuric acid and measured at 2yo. The same applies hereinafter) 2% by weight of 2.60% borocaproamide was mixed and this was melt-extruded at 240°C using a 4-meter extruder to continuously form an unstretched film with a thickness of 200°C. Gelled substances began to be mixed into the film after about 2 hours, and their number gradually increased until it became impossible to discharge the film from the extruder after 5 hours. In this way EVO
Although mixtures of H and polycaproamide have extremely excellent characteristics, they currently have fatal defects that prevent them from being put into practical use.
Therefore, the present inventors investigated the EVOH of polycaproamide.
As a result of intensive studies in order to obtain a resin composition that maintains the improvement effect and does not exhibit the increase in viscosity during melting as shown by mixed compositions of EVOH and polycabroamide, we found that a specific aliphatic copolymer was used as the polyamide to be blended with EVOH. It has been discovered that the above object can be achieved when polyamide is selected, and the present invention has been achieved. That is, the present invention applies to EVOH60-95
weight% and cabroamide as the main structural unit, and the ratio of the number of methylene groups to the number of amide groups is the formula 5.2≦CH2/N
Aliphatic copolymer polyamide 5~ that satisfies HCOS6.5
A resin composition comprising 40% by weight is provided.

EVOH used in the present invention has an ethylene content of 10 to 45% by weight, a degree of saponification of 90% or more, and preferably an ethylene content of 1
It is a saponified ethylene-pinyl acetate copolymer having a saponification degree of 5 to 4% by weight and a degree of saponification of 95% or more. EVOH with an ethylene content of less than 10% by weight is not preferred because it has poor melt extrudability, tends to be colored when melt-molding a composition with polyamide, and is easily thermally decomposed. On the other hand, the engineered tyrene content is 45
If EVOH exceeds % by weight, the melt extrudability of the composition is good, but the gas barrier properties are poor. Further, EVOH having a degree of saponification of less than 90% is not preferable because the molded product lacks dimensional stability, tends to shrink due to heat, and has extremely low gas barrier properties. Although there is no particular restriction on the degree of polymerization of EVOH, EVOH having an intrinsic viscosity of 0.07 to 0.17 m/m is preferably used in the present invention.

If EVOH with an intrinsic viscosity of less than 0.07 so/ta is used, the mechanical strength of the molded composition will be unsatisfactory, and especially in the case of films, the castability of unstretched films will be poor, resulting in unstretched films with good flatness. This tends to cause uneven stretching. On the other hand, if the intrinsic viscosity exceeds 0.17 m/m, the moldability of the composition deteriorates, and the molding temperature needs to be set at a high temperature, causing thermal decomposition and coloring.
The polyamide used in the present invention is obtained by copolymerizing a caproamide component, which is the main structural unit, with other aliphatic polyamide forming components, and the ratio of the number of methylene groups to the number of amide groups is expressed by the formula
It is an aliphatic copolymerized polyamide that satisfies 5.2SCH2/NHCOS6.5.

The caproamide units in this aliphatic copolyamide are 5
If the amount of copolyamide is less than 5% by weight, the effect of improving the stretchability, hot water resistance, impact resistance, etc. of EVOH will be small. This is not preferred because a composition with excellent properties cannot be obtained. Regarding the amide group concentration of aliphatic copolymer polyamide, the ratio of the number of methylene groups to the number of amide groups (C
Q/NHCO) is required to be within the range of 5.2 to 6.5, and for this purpose, copolymerized units with relatively low amide group concentration, such as dodecamethylene amide units and undecamethylene amide units, are introduced. Must. Ratio C
When an aliphatic copolymer polyamide having a H2/NHCO value of less than 5.2 is mixed by EVO stamping, the viscosity of the mixed composition increases greatly during melting, making continuous molding over a long period of time difficult. On the other hand, the CH2/NHCO value of aliphatic copolymer polyamide is 6.
．． If it exceeds 5, the number of caproamide units in the copolyamide decreases and the effect of improving the drawability, hot water resistance, impact resistance, etc. of EVOH is reduced, which is not preferable. Here, a representative example of the aliphatic copolymerized polyamide used in the present invention includes 90 to 6 parts by weight of at least one selected from caprolactam and 6-aminocaproic acid, laurolactam, 12-aminododecanoic acid, and 11-aminoundecane. A copolymer obtained from 10 to 40 parts by weight of at least one type of acid, i.e., nylon 6/1
2:90/10~60/4 6/11:90/10~
For example, 60/40. These aliphatic copolymer polyamides have a melting point of about 160 to 21,000, which is a relatively low melting point, so there is no need to make the molding temperature of the mixed composition with EVOH very high, and the intention is to suppress thermal decomposition and coloring. The copolyamide of the present invention is also suitable for these reasons. Regarding the degree of polymerization of aliphatic copolymerized polyamide, refer to BVOH.
A relatively low viscosity is preferred in the sense of reducing the melt viscosity of the mixed composition and suppressing an increase in adhesion, and the relative viscosity is usually selected from the range of 1.3 to 3.0. Polymerization methods for aliphatic copolyamides include melt polymerization, interfacial polymerization, solution polymerization, bulk polymerization, solid phase polymerization, and a combination of these methods, with melt polymerization being generally the most suitable. The composition of the present invention is composed of 60-95% by weight of EVOH and 5-40% by weight of aliphatic copolyamide.

The blending amount of the aliphatic copolymer polyamide has a significant effect on the gas barrier properties and stretchability of the composition, and if it is less than 5% by weight, the stretchability will not be sufficient, while if it exceeds 4% by weight, the gas barrier properties will deteriorate. Undesirable. For example, when the composition of the present invention is used as a film, from the viewpoint of obtaining a film with extremely high gas barrier properties, it is preferable that the amount of polyamide blended is small. However, when the amount of the aliphatic copolymerized polyamide reaches 5% by weight, it becomes possible to uniaxially stretch the film at a high magnification over a wide temperature range, and the film strength also increases. Furthermore, surprisingly, compared to an unstretched film made of EVOH alone, the gas barrier properties do not deteriorate at all, but rather are improved. Next, when the amount of the aliphatic copolymer polyamide reaches 1% by weight, biaxial stretching becomes possible, and the gas barrier properties do not deteriorate due to the effects of orientation and crystallization of polymer chains due to stretching. Both sequential biaxial stretching and simultaneous biaxial stretching are possible for biaxial stretching, and it is practically preferable to use a film stretched at an area ratio of 4 to 230%. The method of mixing EVOH and aliphatic copolymer polyamide is not particularly limited and any commonly known method can be used. A method of melt-kneading using an extruder is suitable.

It is also possible to explore a method in which uniformly mixed pellets are kneaded directly in a molding machine and then molded without being kneaded in advance in an extruder. The composition of the present invention is mainly used for packaging materials such as films, sheets, tubes, and plastic containers, but it may of course be used for other purposes as well.

When molding the composition of the invention, conventional extrusion molding, blow molding, etc. can be applied, and in either case, stable continuous molding is possible without the generation of gelled products over a long period of time. For example, to produce a single film from the composition of the present invention, it is usually first extruded in a molten state from a T-die head of a presser, and then a known casting method, typically an air knife casting method, an electrostatic application method, or the like.
An unstretched film is obtained by cooling and solidifying on a casting drum using a method such as a vacuum chamber method. Subsequently, this unstretched film is stretched in at least one direction.
Normally, sequential biaxial stretching in the order of longitudinal stretching and transverse stretching is preferred from the viewpoint of productivity, but simultaneous biaxial stretching is also possible, and the stretchability is extremely good. Further, it is preferable to perform heat treatment after stretching in order to maintain dimensional stability and hot water resistance, and tension heat treatment or relaxation heat treatment is effective. The film made of the composition of the present invention has excellent gas barrier properties, hot water resistance, oil resistance, transparency, impact resistance, etc., and has extremely high utility value alone, but it can be used by laminating other thermoplastic resins. It is possible to add more film properties. The film properties added to such a laminated film vary depending on the type of thermoplastic resin laminated. For example, laminating polyolefin resin can significantly reduce water vapor permeability, and laminating polyester can significantly improve heat resistance. It can withstand high-temperature retort processing. In the case of these laminated films as well, it is preferable to stretch them under appropriate conditions to take advantage of their good stretchability. In addition to the same advantages as the above-mentioned film, the sheet formed from the composition of the present invention has an advantage of excellent deep drawability, and is suitable for forming tubes and hollow molded products (containers) by blow molding. It is possible to carry out two-way stretch blow molding and has the advantage that the molded product has excellent dimensional stability and creep resistance. In addition, when molding a sheet or a blow-molded product, the molded product can be made by laminating other thermoplastic resins in the same way as in the case of the above-mentioned film. The composition of the present invention may contain other ingredients such as pigments, heat stabilizers, antioxidants, etc., as long as they do not impair its properties, moldability, etc.
Crystallization promoters, solvents, fillers, plasticizers, etc. can be added and introduced.

The present invention will be explained in further detail by giving examples below.

The physical property values in each example were measured according to the following methods. 01 Oxygen permeability film under 20qo, 100% RH conditions, OXY-
Measurement was performed using TRANIO0 (manufactured by Modem Controls).

Units are per sheet: cc/, 2 r and thickness 0.
Per side: cc/24r/0.1 rib. [2)
Boil test After the film was boiled (held in boiling water for 3 minutes), it was taken out and changes in the film were observed.

The evaluation is ○: There is no change in flatness, transparency, properties, etc. before and after treatment, Δ: The film surface has unevenness and the flatness is poor, ×: The flatness is extremely poor.

[31 Stretchability The condition of the film was observed.

The evaluations are: ○: Uniform stretching and good transparency; Δ: Some stretching unevenness; ×: Film tearing or stretching unevenness occurs during stretching; layer peeling occurs in the laminated film, resulting in poor stretching. (4) Charpy impact strength A film measuring 10 feet wide x 10 feet long was set in a Charpy impact tester (manufactured by Toyo Seiki Seisakusho), and tested according to JISB-777.
Impact rupture energy was measured according to method 2.

{5} The thickening gel characteristic composition is melt-extruded from an extruder to continuously produce an unstretched film. It was measured.

Note that parts and percentages in the examples indicate parts by weight and percentages by weight, respectively.

Example 1 Ethylene content 33%, saponification degree 99%, intrinsic viscosity 0.1
Polyamides A to E shown in Table 1 were blended in the amounts shown in Table 1 to EVOH having a melting point of 170°C.

The details of polyamides A to E are as follows.

Polyamide A (6/12; 80/20)...Copolyamide polyamide B (6/11; 70/3), which is a copolymerized polyamide obtained by melt polymerizing 8 caprolactam and 2 golaurolactam.
0)... Copolyamide polyamide C obtained by melt polymerizing 7 caprolactam and 30 parts of 11-aminoundecanoic acid (6)... Homopolyamide polyamide D obtained by melt polymerizing caprolactam (6/12; 50/50) …
A comparative example of a polymerized polyamide obtained by melt polymerizing 5 parts of caprolactam and 5 parts of laurolactam (CH2/NHCO ratio is above the upper limit) is shown.

) Polyamide E (6/610; 40/60)... A copolymerized polyamide (CH
A comparative example will be shown in which the caproamide unit is not the main component even if the 2/CON daily ratio is within the specified range.

) Each composition (M.1 to 11) was extracted from the extruder with 22
000 to continuously form an unstretched film with a thickness of 200.

No. Nos. 1 to 7, 10, and 11 did not generate gelled substances on the film surface even after continuous molding for two feeding hours or more, and unstretched films with excellent flatness and transparency were obtained.
No. 8 is about 2 blessings, No. In case No. 9, gelled substances were mixed into the film after about 5 hours, making it impossible to form a film. Next, T.
M. Using a Long film stretcher,
Each of the above-mentioned unstretched films was stretched 2.5 times in the machine direction and then 4 times in the transverse direction at 15,000 mm, and the stretchability was evaluated and the physical properties of the stretched films with a thickness of 20 threads obtained were measured. I did it.

These results are shown in Table 1. As shown in Table 1, the gunwale. Films Nos. 1 to 5 had extremely good stretchability, and the stretched films also had excellent physical properties. On the other hand, the gunwale. 6,
Films Nos. 7, 9, 10, and 11 had extremely poor stretchability, and the films broke during stretching, making it impossible to obtain the desired stretched films. Also M. Film No. 8 had good stretchability, but the gas barrier properties of the resulting stretched film were inadequate. From these results, it is clear that continuous melt molding is possible, that stretchability is good, and that a stretched film with well-balanced physical properties is obtained by using EVO. The composition of the present invention that satisfies the requirements (Ship.1 to 5)
) is clearly possible.

Table 1 Example 2 EVOH and nylon 6/12:8 used in Example 1
Using a 0/20 mm copolymer, 25% of the copolymer was mixed with an EVO stamp and then melt extruded to obtain an unstretched film with a thickness of 200 mm.

This unstretched film was first subjected to longitudinal stretching using a roll-type longitudinal stretching machine, then fed into a tenter, transversely stretched, and then subjected to tension heat treatment. By changing the stretching conditions and heat treatment temperature,
When we evaluated the stretchability and measured the characteristic values of the obtained stretched film, as shown in Table 2, both the stretchability and gas barrier properties were good, and it also had excellent mechanical strength and was extremely resistant to boiling water. A film with high practical value was obtained. Example 3 No. of Example 1 The unstretched film with a thickness of 200 mm adjusted in step 2 was stretched at 140 qo in the longitudinal and transverse directions in step 4. After simultaneous two-hoe stretching of Orion, 2% relaxation heat treatment was performed at 160q0, which showed good stretching properties, and the oxygen permeability of the obtained stretched film was 12 cc/sheet.
It was an excellent value of 24 hours.

Claims (1)

[Claims] 1 Saponified ethylene-vinyl acetate copolymer 60-95
% by weight and caproamide as the main structural unit, and the ratio of the number of methylene groups to the number of amide groups satisfies the formula 5.2≦CH_2
A resin composition comprising 5 to 40% by weight of an aliphatic copolymer polyamide satisfying /NHCO≦6.5.