JPS5896527A - Method of blow molding of crystalline thermoplastic resin - Google Patents

Abstract

PURPOSE:To obtain a molded item excellent in solid state properties such as surface gloss, by carrying out the blow molding of a crystalline thermoplastic that is melted in such a manner that said thermoplastic is injected into a mold having a particular surface temperature. CONSTITUTION:A crystalline thermoplastic (e.g. a crystalline polyolefin resin) is injected into the mold having a surface temperature in the range represented by the formula II : Tc-T1-DELTAT< mold surface temperature <Tc+T2(I) wherein Tc denotes the crystallizing temperature of the resin, T1 is 30 deg.C, T2 is 10 deg.C, and DELTAT is a value represented by the formula (II): DELTAT=-12.7 log 10 -15.2+25t (II) wherein lambda is the value of the heat conductivity of the heat insulating layer in cal.cm<-1>.sec<-1>. deg.C<-1>, and it is the thickness of the heat insulating layer in cm, and is subjected to the blow molding.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a blow molding method for crystalline thermoplastic *81. More particularly, the present invention relates to a method for blow molding a crystalline thermoplastic resin that provides a molded article with improved surface gloss and other physical properties.

Hollow molded products made of crystalline thermoplastic resins, particularly crystalline lyolefin resins, have various useful uses, but their surface gloss is not satisfactory. Improvement is desired. One way to improve this is to use the electrical properties of the molded resin material.
Since this may impair the inherent properties of the molded resin material, it is preferable to improve the surface gloss by devising a molding method.

As a molding method for hollow molded products with excellent surface gloss,
A resin paint or a lubricating agent using adhesive is applied to the inner surface of the metal, consisting of a three-layer structure: an undercoat layer that serves as an instant heat insulation layer, an intermediate coat layer that serves as a slight elastic layer, and a top coat layer that serves as a mirror surface layer. (Japanese Unexamined Patent Application Publication No. 51-109065) or a blow molding method using a mold in which all or a part of the blow cavity has a heat insulating structure and the molding surface of the heat insulating structure part is a mirror finish. (Unexamined Japanese Patent Publication No. 51-84925)
etc. have been proposed.

Although the surface gloss of hollow-shaped products may be improved in this way, the use of a lubricant cloth or a mold with a heat-insulating mirror surface makes the molding process easier. We may make things complicated, but we never make them easy. Regardless of these methods, it is a well-known fact that the surface gloss of a molded product can be improved by simply increasing the gold surface concentration, not only in blow molding but also in injection molding. In that case, as described in the patent publication bulletin of the latter, it is said that glossiness can be improved by making the mold temperature, which is normally cooled below 20°C, equal to the parison temperature. The problem is that it takes time to cool the product, reducing operational efficiency.

The present inventors investigated the relationship between the surface temperature of gold and the surface gloss of a hollow molded product, and found that when the metal temperature was raised to a temperature almost equal to the parison temperature, the surface gloss actually decreased, as described above. By blow molding a crystalline thermoplastic resin, especially a crystalline polyolein resin, by setting the surface temperature of the gold layer to a specific temperature lower than that, not only the surface gloss but also other physical properties can be improved at the same time. It has been found that a hollow molded product can be obtained.

Therefore, the present invention relates to a method for blow molding a crystalline thermoplastic resin, and in the blow molding, a molten crystalline thermoplastic resin is molded using the following formula (
This is carried out by injecting into a mold having a surface temperature within the range specified in 1) and performing blow molding.

To-'! +-ΔTku Mold surface temperature (Tc +T2-Δ
T... (1) Tc: Crystallization temperature Ts: 30°C Tz: 10°C Whip: Correction value Δ due to providing a heat insulating layer on the mold surface? --12,77Ogλ-15.2+25t
−・・−(Riyo: Thermal conductivity of the heat insulating layer (哄−, sec,
, 1@,) t: Thickness of the heat insulating layer clR) The thermoplastic resins to be blow molded include low density polyethylene (high pressure method, medium pressure method, low pressure method), medium density polyethylene, high density polyethylene, polypropylene. (homopolymers, copolymers, Plutz copolymers), crystalline polyoleains such as poly(1-butene) and poly(4-methyl-1-pentene), ethylene-vinyl acetate copolymers, polyamides, polyesters, etc. Among them, crystalline polyolefin resins are particularly preferred because they not only improve surface gloss but also impact strength.

When these crystalline thermoplastic resins are blow-molded using a metal material having a surface temperature within a specified range, the surface gloss of the hollow-molded products is improved. This is similar to the case of , but the unexpected effect is that other physical properties are also improved at the same time. The effects of improving various physical properties, specifically tensile properties such as yield stress, breaking stress, and elongation at break, buckling strength, hardness, and drop strength, are particularly important for crystalline polyolefins among crystalline thermoplastic resins. This is noticeable in the case of resin.

Moreover, in the case of crystalline polyolein resin, there is a peak in the mold surface temperature that should be set to obtain good surface gloss, and the temperature at this peak varies depending on the material that makes up the mirror surface of the gold layer. For example, the temperature is 108°C in the case of a stomach-stomach-treated surface, and 90°C in the case of a heat-insulating mirror surface that can be used in the present invention, such as an enamel-finished surface. A mold having a mirror surface with a buffed surface, a niboxi coating, or an acrylic coating can be used at an appropriate predetermined temperature. This means that a temperature lower than the gold amount temperature, which was conventionally set only for the purpose of improving gloss,
This has been shown to have extremely positive effects.

As described above, the mold surface temperature is set within the range defined by the following equation (1).

Tc -T1-Todoroki T〈Mold surface temperature (TO+ T2-◆
T... (1) Here, To is the crystallization temperature, using a differential scanning calorimeter (DIO), AITM D
-3417, an exothermic curve and an endothermic curve were determined, and the respective peak temperatures were defined as the crystallization temperature (To) and melting point (Ta). T and T2' are numerical values indicating the temperature range in which suitable surface gloss and physical properties can be obtained; TI is 30°C, preferably 20°C, and T2 is 10°C, preferably 5°C. ΔT is the surface of the same material as the mold,
For example, if the surface has a puff finish or mirror finish, it is set to 0, and if you use something with a lower thermal conductivity than the mold, such as an enamel finish or a metal lid with pheasant-rotting, this is the correction value. is defined by equation (2).

AT −−12,7togλ−15.2 + 25t
-...- (2) Here, 1 is the thermal conductivity of the heat insulating layer (Cd-/(1g1.5eC-dog), and t is the thickness of the heat insulating layer).

On the other hand, if the mold surface temperature is outside the range of formula (1) above, a hollow molded product with excellent surface gloss cannot be obtained.

The blow molding machine used in the method of the present invention may be one of various known extrusion machines as long as it has a mold that can be adjusted to the above-mentioned temperature range, such as a complete screw set, a ram type, an accumulator type, and a screw intin type. Any of the following blow molding machines can be used. Further, the blow molding die used in the method of the present invention has a temperature s that can be adjusted within the above temperature range.
vy**.

For example, a metal lid with a temperature control mechanism such as steam heating, electric heating, high frequency heating, or oil heating may be used, and a mold made of one or more alloys of iron, aluminum, chromium, zinc, etc. Can be used.

In the present invention, except for using Venus adjusted to the above-mentioned temperature range, a normal method is used, that is, a crystalline thermoplastic resin is prepared at a temperature range suitable for each, e.g., about 160 to 240 °C for polyethylene, Approximately 240 for polyamide
A blow molding die heated after melting at ~280°C,
For example, by extruding a molten parison through a rad die or spider die into a cloth, blowing pressurized gas into a metal tube adjusted to the above temperature range, and taking it out after the resin used has solidified, surface gloss and impact strength can be improved. Excellent hollow molded products can be obtained.

As described above, although the method of the present invention requires a little longer molding time than the conventional method, the obtained hollow molded product has significantly superior surface gloss and improved tensile strength compared to the conventional method. Moreover, polyolein is a molded product with improved buckling strength and impact strength, and is suitable for fields where appearance is important, such as automobile-related parts, household electrical appliances, etc.
Suitable for use in packaging containers, cosmetic containers, furniture, tableware, tanks, etc.

Next, the present invention will be explained with reference to examples.

Example 1 A metal lid for molding an inner bottle was prepared, with the inner surface of the mold mirror-finished by chrome plating with a thickness of 20 seconds, and high-density polyethylene (Tamashi Petrochemical Products Hizex 8000) i
Tm: 128.4℃, To: 114.5℃)
After melting in a 451 diameter extruder with a set temperature of 190°C,
- Using a blow molding die with a set temperature of 190° C., the resin was injected at a temperature of 206° C. into a mold set at the indicated surface temperature shown in Table 1 below, and a 12 ounce inner bottle was blow molded.

Example 2 In Example 1, instead of the 20 μm thick PM plating, a metal shoe for molding an inner bottle was used which had a mirror finish with a 400 μm thick Ho-4 finish.

Implementation H3 Prepare a cylindrical bottle molding lid whose inner surface of the mold has been mirror-finished with 20 J chrome plating, and use crystalline polypropylene (Tamashi Petrochemical Products Polypro 8B 210).
j 2m: 161.1 ℃, 126
．． 1°C, To: 111.5°C) was melted in a 45-diameter extruder with a set temperature of ZOO°C, and then the surface temperature was set to the specified surface temperature shown in Table 2 below using a blow molding die with a set temperature of 210°C. The resin was injected into a mold at a resin temperature of 203°C, and a 400 mg cylindrical bottle was blow-molded.

Example 4 In Example 3, a cylindrical bottle mold was used which had a mirror finish with a 400 s thick enamel finish instead of the 20 μm thick chrome plating.

Example 5 A hot panel panel was prepared in which the inner surface of the mold was polished to a mirror finish with a thickness of 20 μm, and polyamide (Unitika product Unitika Naipun xxlo3o; 7 pieces: 219
．． 3℃, To: 182.4℃) set temperature 250℃
After melting in a 90cm diameter extruder, the temperature is set at 260°C.
Using a hollow molding die, the resin is injected at a temperature of 220°C into a metal lid set at the indicated surface temperature shown in Table 3 below.
It was blow molded into a panel measuring 520 x 340 x 10 cm.

Example 6 In Example 5, poly(4-methyl-1-pentene) (Tamashi Petrochemical Products TPX MX) was used instead of polyamide.
002 E Tm: 220°C, To: 195°C
) was used.

Various physical property values of the molded articles molded in each of the above Examples were measured in the following manner.

Glossiness: J-K5Z-8741, angle of incidence 45゛Tensile properties:
A51TM D-638 Buckling strength: JXB K-7208 Surface hardness 2! iTM D-2240, Type D Drop strength: In the case of polypropylene, fill 400-cylindrical bottles with water, seal the back end, and drop 10 bottles at a time onto a concrete surface from a height of 14 m. In the case of polyethylene, the breakage rate of polyethylene is determined by dropping it vertically, and then filling a 12-ounce square bottle with water, sealing the back end, and dropping the bottle vertically onto a concrete surface from a certain height. , if the bottle breaks, the drop height is lowered by 803 and the next bottle is dropped, while if the bottle does not break, the drop height is increased by 30 cI11 and the next bottle is dropped, and such a drop test is performed. The test was carried out on 30 bottles, and the height at which 15 bottles broke was determined and the drop strength was taken as the falling strength. A styrene copolymer resin (Stylac A-3190'' manufactured by Shio Dow) or a polyphenylene oxide resin (Zylon soo H manufactured by Asahi Dow) were used and panels were blow molded from these non-grade thermoplastic resins.

The gloss of the obtained blow-molded panel increased as the surface temperature of the molded metal lid increased, but the values of various tensile strengths, hardness, and Izod impact strength remained almost unchanged.

As can be seen from the above results, for crystalline thermoplastic resins, especially crystalline polyolein resins, improvements in various physical properties including glossiness were observed as the surface temperature of the molding die increased; Regarding the thermoplastic resin, almost no changes were observed in other physical properties except for gloss.

Examination of each item of physical property values is as follows.

<1) Glossiness: Regardless of whether it is crystalline or non-crystalline, as the surface temperature of the molding die increases, the surface glossiness of the molded product increases. In particular, in the case of polyolefin resin, a peak is observed in the mold surface temperature, and the temperature at this peak varies depending on the material of the mold surface; in the case of a chrome-plated surface, it is 108 °C,
Moreover, in the case of a 4-finished surface having a lower thermal conductivity, the temperature is 90°C, and in the latter case, not only can this temperature be set lower by about #F15°C, but also the obtained gloss value is higher.

(2) Tensile strength: Except for a slight decrease in the breaking stress and breaking elongation of polypropylene and the breaking elongation of L-lyamide, the tensile strength of crystalline thermoplastic resins increases with increasing surface temperature of the molded metal lid. Show trends. On the other hand, no change was observed in the case of non-quality thermoplastic resins.

(8) Swarf strength: Swarf strength of polyolefin resin increases as the surface temperature of the molding die increases.

(4) Hardness: The hardness of the polyolefin resin shows a tendency to increase as the surface temperature of the molding die increases. (5) II No particular change is observed.

(6) Impact strength: In the case of polyolefin resin, its impact strength increases as the surface temperature of the mold increases.

Procedural amendment (voluntary) October 1982
May 14, 1, Display of the case 1982 Patent Application No. 195452 2 Name of the invention Blow molding method for crystalline thermoplastic resin 1 Person making the amendment Relationship to the case Name of patent applicant Name (588) Mitsui Petrochemical Industries, Ltd. company (
and 1 other person) Osamu Motoyo Address: 50 Ato Building, 1-2-7 Shiba Daimon, Minato-ku, Tokyo
No. 1 No. 5, Subject of amendment (1) The scope of claims is amended as shown in the attached sheet.

(2) On page 3, line 1θ, “JP-A-1972-” was changed to “JP-A-1973-”
Corrected to ``6-''.

(3) Delete "-ΔT" from the first line of page 5 and the seventh line of page 7, respectively.

(4) r logl on page 5, line 7 and page 8, line 1
Correct each J to "10g+o" J.

(6) r(at/z on page 5, line 8 and page 8, line 2)
・5ea-d@g) J respectively r (tllVc
Correct it to "a numerical value expressed as xs・m*o・℃)".

(6) r(cNl) on page 5, line 9 and page 8, line 3
Insert "a numerical value represented by" after J.

(7) In the 7th line, before “preferably 20℃”, “
For ethylene polymers such as high-density polyethylene, insert ".

(8) After “enamel” in the 3rd line of the 7th nobleman, “(mu: 2
X 10-'Cat/cym・110・'C)
Insert J.

(9) After “Kujikishi” in the 3rd line of the 7th nobleman, “(λ:4
．． 2 X 10""at/cm-11O・'C) J
Insert.

α Wei "Example" is corrected to "Experimental example".

(Corrections) No. 9, line 1, page 10, line 10, 1
Line 1, line 14, page 11, line 4, line 5, line 8, line 3 of Shimodate, line 2 of Shimodate, page 12, line 3, page 16, the leftmost column of Table 3 (3 locations), and Page 17, line 2.

(6) After “Chrome” in the first line of page 1O, “(λ:6X
IO-2at//ff1-・C・℃)'' Full insertion through.

(B) After "l14.5℃" on page 10, line 4, ", density: 0.950 g/ai, Mel)
) 20.03 g/10 minutes” is inserted.

(To) Insert the following sentence between page 10, line 9 and line 1θ.

"As shown in the results in Table 1 below, bottles that were blow-molded using molds (46-8) having surface temperatures within the range used in the present invention were excellent in terms of gloss and mechanical strength. (2) Insert the following sentence between lines 13 and 14 on page 10.

"As shown in the results in Table 1 below, bottles that were blow-molded using molds (44-8) having surface humidity within the range used in the present invention were excellent in terms of gloss and mechanical strength. ) After "l11.5℃" on page 11, lines 3-2,
Density: α9109/Ii, Melt flow rate: α5V
Insert "10 minutes".

(b) Insert the following sentence between the third and fourth lines of page 11.

As shown in the results in Table 2 below, bottles made of gold II (44-6) having a surface concentration within the range used in the present invention are blow-molded in terms of gloss and mechanical strength. . (b) Insert the following sentence between #111, page 7, line 8.

``As shown in the results in Table 2, the bottles that were blow-molded using the molds (43-6) having surface temperatures within the range used in the present invention had excellent gloss and mechanical strength. (b) On page 11, line 3, after “enamel finish” there is “(
ΔT-20°C)".

(b) On page 12, lines 3 and 4, ``Then, .

) Add the following sentence at the end of page 13.

"Experimental Example 7 A mold for molding a cylindrical bottle was prepared with a mirror finish of 20 mm on the inner surface of the mold, and was made of high-density polyethylene (Tm j 130.9°C, To: 11 (L4)
°C, density: 0.9587 shoulder, melt flow rate: 0
．． 40 710 minutes) in a 45 m diameter extruder at a set temperature of 190°C, the resin was melted at a temperature of 202°C using a blow molding die at a set temperature of 190°C and placed in a mold set to the indicated surface temperature shown in Table 4 below. It was poured at 0.degree. C. and molded into 300-degree cylindrical bottles.

As shown in the results in Table 4 below, the bottles blow-molded using molds (45-7) having surface temperatures within the range used in the present invention are excellent in gloss and mechanical strength.

Experimental Example 8 In Experimental Example 7, a 400 tId cylindrical bottle mold was used which had a mirror finish with a 400μ thick enamel finish (ΔT-20°C) instead of a 20μ thick chrome plating.

As shown in the results in Table 4 below, the bottles blow-molded using molds (42-5) having surface temperatures within the range used in the present invention are excellent in gloss and mechanical strength.

Experimental Example 9 In Experimental Example 7, another high-density polyethylene (Tll;
133.5℃, 'J''O+ 118.2℃, density + 0
．． As shown in the results in Table 5 below, molds (A4-6
) Bottles made by blow molding are excellent in terms of gloss and mechanical strength.

Experimental Example 10 In Experimental Example 8, the high density polyethylene used in Experimental Example 9 was used.

As shown in the results in Table 5 below, the bottles blow-molded using molds (43-6) having surface temperatures within the range used in the present invention are excellent in gloss and mechanical strength.

Experimental Example 11 In Experimental Example 7, crystalline polypropylene (T+a: 159.8°C, To:
110.6℃, density: 0.9109/j, melt 70
- Ray): 0.50g 710 minutes) was used.

As shown in the results in Table 6 below, the products that were blow-molded using molds (A3-6) having surface temperatures within the range used in the present invention were excellent in terms of gloss and mechanical strength.

Experimental Example 12 In Experimental Example 8, the crystalline polypropylene used in Experimental Example 11 was used instead of high-density polyethylene.

As shown in the results in Table 6 below, the products that were blow-molded using molds (42-6) having surface temperatures within the range used in the present invention were excellent in terms of gloss and mechanical strength.

Above 4! The method for measuring the drop strength of the molded product molded in P test example is as follows.

Experimental Example 7~lO: The molded shoulder was filled with 0°C water and the rear opening was sealed.
Experimental example 11N12: 15 bottles were dropped perpendicularly onto a concrete surface from a height of 10 fn, and the breakage rate was taken as the falling strength. Experimental example 11N12: The molded shoulder was filled with water, the rear opening was sealed, and the bottle was dropped at a certain height. A bottle is dropped vertically onto a concrete surface, and if a bottle breaks, the falling height is lowered by 20 cm and the next bottle is dropped; if the bottle does not break, the falling height is reduced by 20 crn.
Raise it up and drop the next bottle, repeating this kind of drop test 3 times.
The test was carried out for 0 bottles, and the height at which 15 of them broke was determined and used as the falling strength.

〔Attachment〕

Claim 1: A crystalline thermoplastic resin characterized in that the molten crystalline thermoplastic resin is injected into a mold having a surface temperature within the range defined by the following formula (1) and blow-molded. Hollow molding method.

Ta −T , −ΔT × mold surface temperature (Tc + T2
......(1) To: Crystallization temperature T,: 30℃ T, 710℃ ΔT: Correction value ΔT" by providing a heat insulating layer on the mold surface = -12,710g+oλ-15,2+ 25
t -...-(2) λ: Thermal conductivity of the heat insulating layer (φj
・-・O・℃) t: Thickness of the heat insulating layer (cm) 2T is 20℃, and T2 is 5℃ within the range specified by equation (1). Claims in which a mold having a surface temperature is used [#l! The blow molding method described in item 1.

The blow molding method according to claim 1, wherein a crystalline/IJ olefin resin is used as the crystalline thermoplastic resin.

The blow molding method according to claim 1, wherein a mold having a heat insulating layer provided on the surface thereof is used.

In formula (1) in the claims of the petitioner, the right-hand side “−ΔT
'' was deleted in order to avoid such a coefficient, since if such a coefficient were present on the right side, A7-8 of Example 2 and M5-6 of Example 4 would no longer be included in the scope of the claims. .

Claims (1)

[Claims] 1. Crystalline thermoplastic resin characterized by injecting a molten crystalline thermoplastic resin into a mold having a surface temperature within the range defined by the following formula (1) and performing blow molding. Hollow molding method for resin. To-TI-6 metal gourd surface temperature (To+'r=-6 t...4 (1) To: Crystallization temperature T1: 30℃ 'h: 10℃ ΔT: Providing a heat insulating layer on the mold surface Correction value ′ Δchi12.71ogA -15,2+ 25 t
”” (2) 1: Thermal conductivity of the insulation layer (哄 &, se
c, a・g) t: Thickness of the heat insulating layer 3) The mold has a surface temperature within the range defined by equation (1) where 2T is 20℃ and T2 is 5℃. A blow molding method according to claim 1, which is used. 3. The blow molding method according to claim 1, wherein a crystalline polyolein resin is used as the crystalline thermoplastic resin. 4. The blow molding method according to claim 1, wherein a mold having a heat insulating layer provided on the surface thereof is used.