JP3463854B2 - Injection blow molding - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection blow-molded article made of a polyolefin resin, and more particularly to an injection blow-molded article having good moldability when the cold parison method is used.

[0002]

BACKGROUND OF THE INVENTION Injection blow molded articles are generally manufactured by the hot parison method and the cold parison method. In the hot parison method, a parison (preform) in a high temperature state immediately after injection molding is introduced into a split mold, and air is immediately blown into the parison, or after the temperature of the parison is adjusted, air is introduced into the parison. Is a method of blow molding into a predetermined shape. On the other hand, in the cold parison method, an injection-molded parison is once cooled and solidified, and the parison is heated by a predetermined heating means in a separate step and then introduced into a split mold to blow air into the parison to a predetermined temperature. This is a method of blow molding into a shape.

Among the molded products obtained by these methods, those made of polyester resin such as polyethylene terephthalate can be easily molded by any of the hot parison method and the cold parison method. However, a molded product made of a polyolefin resin such as polypropylene or polyethylene is not easy to mold by any of the hot parison method and the cold parison method, and it is particularly difficult to mold it by the cold parison method. In particular, it is extremely difficult to mold a thick flat container or asymmetric container made of a polyolefin resin by using the cold parison method.

By the way, as a conventional technique relating to a polyolefin resin for injection blow molding, for example, those described in JP-A-63-162740 and JP-A-6-179776 are known. Among them, JP-A-63-162740 discloses that the ethylene content is 2
An olefin resin composition having an MFR of 0.5 to 4.0 g / 10 minutes, which comprises 5 to 99% by weight of a propylene resin of 0% by weight or less and 1 to 95% by weight of an ethylene resin having an ethylene content of 75% by weight or more. Things are listed. Further, in JP-A-6-179776, there are two or more DSC melting peaks, the melting range maximum value is 120 to 165 ° C., the half-value width of the melting peak is wider than 10 ° C., and the quarter peak height is 1/4 peak height. Polyolefin molding compositions having a width greater than 15 ° C. are described.

However, JP-A-63-162740
The technology described in the publication is aimed at improving the moldability of the hot parison method. In this publication, there is nothing about the moldability of the cold parison method, especially the moldability of thick flat containers and asymmetrical containers. Not considered. Similarly, Japanese Patent Application Laid-Open No. 6-179776 does not describe any moldability when molding a thick flat container or an asymmetric container by the cold parison method.

Therefore, an object of the present invention is to provide an injection blow-molded article having good moldability when the cold parison method is used. Another object of the present invention is to provide an injection blow-molded product having good moldability for a thick flat container or an asymmetrical container, especially by the cold parison method.

[0007]

Means for Solving the Problems As a result of intensive studies, the inventors of the present invention have paid attention to the relationship between the elastic modulus of a polyolefin resin forming an injection blow-molded article and the temperature, and as a result, have found that the resin whose elastic modulus changes slowly with temperature. Was found to have good formability by the cold parison method, and when further investigation was conducted,
It has been found that the above object can be achieved by an injection blow-molded product made of a polyolefin-based resin having a gradient of decrease in elastic modulus due to melting within a specific range.

The present invention has been made on the basis of the above findings, and is an injection blow molded product obtained by using a cold parison made of a polyolefin resin, the elastic modulus of which is obtained by solid viscoelasticity measurement of the polyolefin resin. E
The following formula (A) in the relation of (Pa) -temperature T (° C )
In represented, range near the slope S is 0-0.2 in elastic modulus decrease due to melting of the polyolefin resin is, and main
Routt flow rate is 1-50g / 10 minutes, above
Flatness (maximum major axis of trunk / minimum minor axis of trunk)
1.15 or more and the thickness of the body is 0.2 to 3.0 m
injection blow molded article, wherein the container der Rukoto of m. Slope S = [(ΔlogE) / (ΔT)] (A) (The slope S in the above formula (A) is a graph in which the logarithmic value of the elastic modulus E is plotted against the temperature T, and the elastic modulus in this graph is Three measurement points of E are taken from the low temperature side, a regression line is obtained for these three points, this work is performed while shifting the measurement points one by one to the high temperature side, and correlation coefficients r ² and The slope is obtained and is the value of the slope in the regression line immediately before the correlation coefficient r ² becomes smaller than 0.95.The correlation coefficient r ² is calculated from the following equation (1).)

[Equation 2]

[0009]

[0010]

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The injection blow-molded article of the present invention is obtained by using a cold parison made of a polyolefin resin. In the present specification, the “cold parison” is a bottomed parison formed by injecting a molten resin into a closed space formed by a male core and a female cavity, and is cooled or cooled. It means a solidified one. Further, in this specification, "injection blow molding" means
Not only a method of sandwiching a heated softened bottomed parison with a split mold and blowing air into the bottomed parison but also a heated softened bottomed parison with a split mold, the bottomed parison It also means a method (injection stretch blow molding) in which a stretch pin is inserted into the inside of the container to stretch the bottomed parison and then blown with air to perform blow molding.

The above polyolefin resin has a gradient S of a decrease in elastic modulus due to melting of the polyolefin resin in the relationship of elastic modulus E (Pa) -temperature T (° C.) obtained by solid viscoelasticity measurement of 0 to 0. It is within the range of -0.2. In the present invention, the slope S is the slope S = from the relationship between the elastic modulus E of the polyolefin resin and the temperature T.
It is obtained from [(ΔlogE) / (ΔT)]. The specific measuring method will be described later. By using such a polyolefin-based resin, it is possible to obtain an injection blow-molded article having good moldability when using the cold parison method, and particularly, the moldability of a thick flat container or an asymmetric container by the cold parison method. A good injection blow molded product can be obtained. More specifically, when the gradient S is less than -0.2, holes are formed in the parison or the molded body is whitened when the parison is blow molded in the split mold. On the other hand, the slope S cannot exceed 0. The reason for this is that the test piece is melted and cut before the carbonization of the polyolefin resin during the measurement due to the temperature rise, or the measurement becomes impossible and the measurement ends. The preferred range of the gradient S is 0 to -0.18, more preferably 0.
It is -0.13.

In the present invention, the elastic modulus E and the slope S are measured as follows. A test piece having a thickness of 50 μm, a length of 37 mm, and a width of 5 mm is attached from the above polyolefin resin between chucks of Solids Analyzer RSA-II (manufactured by Rheometrics) with a chuck distance of 22.5 mm. The initial length of the test piece is the chuck-to-chuck distance after the chuck-to-chuck distance is adjusted so that the load detected by the load cell becomes zero after the test piece is heated / stabilized to the measurement start temperature. Then, a load is applied to this test piece at a frequency of 0.16 Hz, and the elastic modulus E is measured. The elastic modulus E is measured every 30 ° C. to 2 ° C. until the test piece melts and cannot be measured.

The slope S is obtained from the elastic modulus E thus measured. That is, first, as shown in FIG. 1, a graph is prepared by plotting the logarithmic value of the measured elastic modulus E against the temperature T. The elastic modulus E in this graph is measured at three points from the low temperature side, and a regression line is obtained at these three points. This operation is performed while shifting the measurement points to the high temperature side one by one. That is, in the example shown in FIG. 1, first, the regression line L1 is obtained for the points 1 to 3, and then the points 2 to 4 are obtained.
Then, a regression line L2 is obtained, and similarly, the points 3 to 5,
A regression line is obtained for each of points 4 to 6. The correlation coefficient r ² and the slope of each regression curve thus obtained are obtained. Correlation coefficient r
² generally shows that the measurement point of the elastic modulus E tends to depart from 1 as it goes to the higher temperature side, but this correlation coefficient r ² is less than 0.
The slope of the regression line immediately before which it becomes smaller than 95 is adopted as the value of the slope S. In the example shown in FIG. 1, points 8 to 1
The correlation coefficient r ^{2 on} the regression line L8 of 0 is 0.95,
The correlation coefficient r ^{2 on} the regression line L9 of the points 9 to 11 is 0.
Since it is 88, the slope of the regression line L8, which is the regression line immediately before the correlation coefficient r ² becomes smaller than 0.95, is the value of the slope S.

The correlation coefficient r ² of the regression line and the slope S
The value of is statistically calculated from the following equations (1) and (2), respectively.

[0016]

[Equation 3]

[0017]

[Equation 4]

As the polyolefin resin which can be used in the present invention, any one can be used as long as the value of the gradient S is within the above range. Examples thereof include a polymer of ethylene, a polymer of propylene, an ethylene-propylene copolymer, an ethylene-based ethylene-α-olefin copolymer containing one or more α-olefins, and one or more α-olefins. A single polyolefin resin such as a propylene-based propylene-α-olefin copolymer may be mentioned. Also, two or more α
-A resin composition comprising the above propylene-α-olefin copolymer, two or more kinds of olefin polymers and / or different copolymerization ratios, the above propylene-α-olefin copolymer or an ethylene-based resin composition. A resin composition such as a resin composition obtained by blending 30% by weight or less of a resin is also included. That is, in the present specification, the “polyolefin resin” means a single polymer or copolymer in which olefin is used as a monomer component, and a resin composition containing the polymer or copolymer.

As the α-olefin, for example, when the polyolefin resin is a copolymer mainly composed of ethylene, one having 3 to 20 carbon atoms is preferable, and 1-olefin is particularly preferable.
Hexene, 1-octene, 1-peptene and 4-methylpentene are preferred. When the polyolefin resin is a propylene-based copolymer, it preferably has 2 to 10 carbon atoms, and ethylene and 1-butene are particularly preferable. The copolymerization ratio of α-olefin to propylene or ethylene is preferably 2.5 to 15. Α-
One kind or two or more kinds of olefins are used.

Among the above polyolefin resins, (a)
Propylene-based propylene-α-olefin copolymer containing one or more α-olefin, (b) two or more α
A resin composition comprising an olefin polymer and / or two or more copolymers of the above (a) having different copolymerization ratios; or (c) the copolymer of the above (a) or the resin of the above (b). It is preferable to use a resin composition obtained by blending 30% by weight or less of an ethylene-based resin with the composition because the moldability is further improved. In particular, a propylene-based propylene-ethylene copolymer, a propylene-butene copolymer, a propylene-ethylene-butene copolymer, and a resin composition containing these two or more copolymers, and further the above-mentioned copolymer and / or Alternatively, it is preferable to use a mixture obtained by adding low-density polyethylene to the resin composition. When two or more kinds of resins are mixed and used, a method such as dry blending and feeding to a molding machine, a method of previously melting and kneading with a twin-screw kneader and pelletizing, and feeding to a molding machine are possible. . The method (1) is more preferable in terms of manufacturing cost, and the method (2) is more preferable in terms of moldability, appearance and the like.

The polyolefin resin has a melt flow rate (hereinafter referred to as "MFR") of 1 to 5 from the viewpoint of moldability in addition to having the gradient S in the above range.
It is in the range of 0 g / 10 minutes, preferably 1 to 30 g / 1
Area by near 0 minutes. More specifically MFR injection molding and less than 1 g / 10 min is difficult, blow moldability may turn poor exceeds 50 g / 10 min. MFR is JIS-
According to 7210 (Condition 14), it was measured under a load of 21.18 N and a temperature of 230 ° C. Incidentally, MFR
Means the MFR of the polymer or copolymer when the polyolefin resin is a single polymer or copolymer, and the resin composition when the polyolefin resin is a resin composition. The MFR of a product.

Various additives can be added to the polyolefin resin as long as the gradient S satisfies the above range. Examples of such an additive include a crystal nucleating agent such as a sorbitol-based or organic phosphate-based agent, an antioxidant, an antistatic agent, a slip agent, an ultraviolet absorber, a colorant, a pigment and a filler. These additives are contained in the polyolefin resin in an amount of 10% by weight or less, particularly 5% by weight.
It is preferable that the following components are blended.

Next, a preferred method for producing the injection blow molded article of the present invention using the above polyolefin resin will be described. First, the molten polyolefin resin is injected into a closed space composed of a male core and a female cavity to form a bottomed cylindrical parison. The injection molding conditions and the like are the same as in the usual case. The parison is taken out of the mold and cooled (this parison is generally called a cold parison). The wall thickness of the parison is 1 to 20 mm, particularly 2 to 10 mm, although it may be restricted by the design of the wall pressure of the molded product and the diameter and shape of the screw part when molding a bottle as the molded product. From the viewpoint of molding cycle and moldability such as transparency, strength, and meat pressure distribution of the container, it is preferable.

Next, the parison is heated in the heating zone to a temperature at which blow molding is possible. As a heating means, a method of heating from the outside of the parison with an infrared heater, a radiant heater such as far infrared rays, or a method of inserting a temperature-controllable core into the parison and heating from the inside is used alone or in combination. can do. Further, in the heating zone, it is preferable to uniformly heat the parison by rotating the parison relative to the heating means. If the parison has a portion such as a screw portion that does not require further deformation, the portion is heat-shielded before heating. The heating temperature of the parison depends on the kind of the above polyolefin resin, but it is generally preferably 1 to 20 ° C., especially 5 to 15 ° C. lower than the melting point of the polyolefin resin. This heating causes the parison to be in a softened state except for the screw portion. The parison heated in this way except for the screw portion is introduced into the blow molding portion composed of a split mold. Then, high pressure air is blown into the parison for blow molding. Alternatively, after low-pressure air is blown, high-pressure air is blown to blow-mold. After cooling until the shrinkage is stable, the molded product is taken out from the split mold to obtain a molded product whose surface has the same shape as the shape of the cavity inside the split mold. The air pressure is the same as in the usual case, and is generally about 2 × 10 ⁶ to 4 × 10 ⁶ Pa for high pressure air and about 1 × 10 ^{4 to} 5 × 10 ⁵ Pa for low pressure air. In the case of injection stretch blow molding, a stretch pin is inserted into the parison introduced into the split mold for stretching (stretching), and then high pressure air is blown into the parison for blow molding. The draw ratio in this case is an area ratio of 1.2 to
70 times (1 to 10 times in the vertical direction, 1.2 to 7 in the horizontal direction)
Double), particularly 1.8 to 20 times (1.2 to 4 times in the longitudinal direction and 1.5 to 5 times in the lateral direction), the parison design and blow moldability (stretchability) are good. It is preferable in that

The above surface magnification is the parison shown in FIG.
(Preform) 10 height (excluding screw part 11) a and
And the average diameter b, and the height of the molded body 12 shown in FIG.
From the values of c (excluding the screw part 11) and the outer diameter d of the molded body,
It is calculated from the following formula. Area magnification = (c / a) x (d / b) In addition, as shown in FIG.
If the wall thickness of 10) has changed, the minimum wall thickness t₁
And maximum wall thickness t₂And the average wall thickness (t₁+ T ₂) /
The average diameter in the part 13 in which 2 is present [ie the part
[Average value of inner diameter and outer diameter in 13]]
The value.

Molded products having various shapes can be obtained by the method described above. In particular, in the present invention, a container having a flat shape and / or an asymmetric shape, which has been extremely difficult to be molded using the cold parison method in the past (for example, a bottle having a flat and asymmetric shape as shown in FIG. A flat bottle as shown in 4) can be easily obtained. Moreover, in the case of a flat-shaped container, a container having a flatness ratio of 1.15 or more, which is a ratio of the maximum major axis of the body / the minimum minor axis of the body, can be easily obtained. Moreover, the thickness of the body is 0.2 to 3.
A flat and / or asymmetrical container having a thickness of 0 mm, particularly 0.2 to 1.5 mm, can be easily obtained. Further, since the injection blow-molded product of the present invention is formed of the above-mentioned polyolefin resin having good moldability, it has a uniform wall thickness, good squeeze property, and high buckling strength.

[0027]

EXAMPLES The present invention will be described in more detail below with reference to examples, and the effectiveness of the present invention will be illustrated. However,
It goes without saying that the scope of the present invention is not limited to the above examples.

[Examples 1 to 7 and Comparative Examples 1 to 4] Resins shown in Table 1 were used, and the wall thickness was 5.7 mm and the length was 10 mm.
An 8 mm bottomed cylindrical parison was injection molded. However, in Examples 2 to 4, two kinds of resins were dry-blended at the ratio in parentheses in Table 1 and supplied to the molding machine. The parison was heated from the outside with an infrared heater to a temperature for blowing while rotating. Then, the parison is introduced into a split mold, and a stretch pin is further inserted into the parison to
While longitudinally stretching 3 times, low pressure air of 2 × 10 ⁵ Pa was blown, and then high pressure air of 2.6 × 10 ⁶ Pa was blown to blow-mold. After cooling, the bottle was taken out from the split mold to form a bottle having a flatness of 1.7 with a flatness of 1.7.
The average thickness of the body of this bottle was 0.6 mm (range: 0.
2 to 1.2 mm). The moldability when each resin is used is shown in Table 1 together with the gradient S of each resin. The moldability was evaluated by the breadth of the parison temperature range in which blow molding was possible. The parison is heated while changing the heating conditions, and then the parison is introduced into a mold for blow molding. At this time, if the heating conditions are appropriate, the target shape can be blow-molded, and if the heating conditions are not appropriate, the target shape cannot be reached due to breakage during the blow-molding. This heating condition is obtained by measuring the temperature of a specific part of the parison (the center part in the height direction of the parison) immediately before the introduction into the mold with an emissivity thermometer at an emissivity of 0.9. By the above test, the moldable temperature at which the target shape can be blow molded while changing the parison temperature under heating conditions was investigated, and the following moldability was judged. Judgment of moldability in Table 1 ... Stable blow molding is possible up to the target shape even when the temperature range is touched. X ... Stable blow molding is impossible up to the target shape when the temperature range is touched. The range of temperature fluctuation is 0 to less than 30 ° C.

[0029]

[Table 1]

As is clear from the results shown in Table 1, the bottles of the present invention (products of the present invention) formed from a polyolefin resin having a gradient S within a specific range using the cold parison method are comparative examples. It is understood that the moldability is extremely good as compared with the bottle of No. Although not shown in the table, the bottles of the examples (the products of the present invention) had good squeezeability and high buckling strength.

[0031]

As described above in detail, according to the present invention,
When the cold parison method is used, an injection blow molded product having good moldability can be obtained. Further, according to the present invention, an injection blow-molded article having good moldability for a thick flat container or an asymmetrical container by the cold parison method can be obtained. Further, according to the present invention, an injection blow-molded article having good squeeze property and high buckling strength can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between an elastic modulus E of a polyolefin resin and a temperature T.

2 (a) to 2 (c) are schematic cross-sectional views showing dimensions of a parison (preform) and a molded body, which are used for calculating the surface magnification of injection blow molding.

3 (a) and 3 (b) are respectively a front view and a side view showing an embodiment of the injection blow-molded article of the present invention.

4A and 4B are a front view and a side view showing another embodiment of the injection blow-molded article of the present invention, respectively.

[Explanation of symbols]

10 parison (preform) 12 molded body

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiji Sakamoto 2606 Akabane Kai, Haga-gun, Tochigi Prefecture Kao Corporation Research Institute (56) Reference JP-A-63-162740 (JP, A) JP-A-9-52278 ( JP, A) JP 59-140033 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29C 49/00-49/80 C08L 23/14 C08L 23/18

Claims (2)

(57) [Claims] 1. An injection blow-molded article obtained by using a cold parison made of a polyolefin resin, comprising:
Obtained by solid viscoelasticity measurement of the polyolefin resin,
Modulus E (Pa) - in relation to the temperature T (° C.), the following
The gradient S of the elastic modulus decrease represented by the formula (A) accompanying the melting of the polyolefin resin is in the range of 0 to -0.2.
And a melt flow rate of 1 to 50 g / 10 minutes
The above-mentioned molded body has a flatness (maximum major axis of trunk / minimum minor axis of trunk)
A container having a thickness of 1.15 or more, wherein the thickness of the body of the container is
An injection blow molded product having a diameter of 0.2 to 3.0 mm . Slope S = [(ΔlogE) / (ΔT)] (A) (The slope S in the above formula (A) is a graph in which the logarithmic value of the elastic modulus E is plotted against the temperature T, and the elastic modulus in this graph is Three measurement points of E are taken from the low temperature side, a regression line is obtained for these three points, this work is performed while shifting the measurement points one by one to the high temperature side, and correlation coefficients r ² and The slope is calculated and is the value of the slope on the regression line immediately before the correlation coefficient r ² becomes smaller than 0.95.The correlation coefficient r ² is calculated from the following equation (1). 2. The polyolefin resin is (a) a propylene-α-olefin copolymer mainly composed of propylene,
(B) A resin composition comprising a polymer of two or more kinds of α-olefins and / or two or more kinds of the copolymers of the above (a) having different copolymerization ratios, or (c) a copolymerization weight of the above (a). Combined or ethylene resin to the resin composition of the above (b) 3
0 wt% blending less made of synthetic resin composition according to claim 1 injection blow molded article according.