JPS6286039A - Thermoforming polypropylene resin sheet - Google Patents

Abstract

PURPOSE:To obtain a resin sheet having high melt tension during molding and improved flavor properties, by extruding polypropylene contg. an org. phosphite compd. and a specified phenolic antioxidant into a sheet. CONSTITUTION:A resin sheet is obtd. by extruding a polypropylene resin compsn. contg. 0.02-0.5pts.wt. antioxidant (A) selected from among org. phos phite compds. and 0.02-0.5pts.wt. phenolic antioxidant (B) selected from among compds. of the formula or tetrakis-[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate]methane per 100pts.wt. resin compsn. composed of 70-100wt% polypropylene and 0-30wt% polyethylene. Examples of said antioxidant (A) are tris-(mono-di-nonylphenyl) phosphite, tris(2,4-di-t-butylphenyl) phosphite, etc.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a polypropylene resin sheet for thermoforming.
More specifically, it relates to a resin sheet for aging molding that has high melt tension during molding and is suitable for food containers with improved flavor properties such as odor and taste.0 <Prior Art> Polypropylene has good processability. Due to its excellent flexibility, high softening point, and high rigidity and hardness, it is industrially produced, molded into various shapes, and used in many fields of application. One of them is Makabe molding, which is molded into film or sheet shape.
Polypropylene is widely used for various containers, etc. after being subjected to secondary forming by air forming and hot plate heating. When performing secondary forming processing by molding, etc., the sheet sag during sheet heating is large, resulting in molded products with wrinkles and uneven wall thickness. In order to improve the above-mentioned drawbacks, methods of blending polypropylene [polyethylene or ethylene-propylene copolymer, etc.] have been carried out (Japanese Patent Laid-Open No. 55-1
No. 08488, Japanese Unexamined Patent Publication No. 189445/1983,
JP-A-56-41287, JP-A-58-9874
．． Publication No. 2, Japanese Unexamined Patent Application Publication No. 85684, etc.

However, with this method, the effect of improving the melt tension during heating of the sheet was still insufficient, and there were problems with thermoformability when forming complex shapes, exploring shapes, or thinning. It is subjected to a secondary molding process using a molding method and is widely used for food packaging containers and trays for foods, frozen desserts, lactic acid drinks, etc., but it also has the problem of worsening the flavor (odor and taste) of the food contents. had.

The main reason for this is that butylated hydroxydoluene (BHT) is conventionally added to polypropylene thF as an antioxidant, but when exposed to high temperatures during sheet molding and secondary molding, a new odor occurs. This is thought to be due to the occurrence of odor and its transfer to the food contents.

In addition, diphenybentaerythritol μ is added to polypropylene.
It is known that addition of schifosphite and phenolic antioxidants prevents polymer decomposition during high processing (Japanese Patent Application Laid-Open No. 106879/1983). There was no mention of it at all.

<Problems to be Solved by the Invention> Under the current situation, the problems to be solved by the present invention, that is, the purpose of the present invention is to solve the problems in secondary forming processing such as vacuum forming, pressure forming, hot plate heating pressure forming, etc. An object of the present invention is to provide a polypropylene resin sheet that has a high melt tension when heated and has improved flavor properties for food packaging containers and trays obtained by secondary molding.

<Means for Solving the Problems> The invention is based on 100 parts of a resin M composition consisting of 70 to 100% by weight of polypropylene and polyethylene O to 30M, and a compound selected from Arigo futsphite compounds. 1 @ or two or more antioxidants (hereinafter referred to as "antioxidant A") 0
．． 02 to 0.5 parts by weight and the general formula fil -Bu (Ct3, R1 is a methyl A/ group or a t-butyl group,
R2 represents a chain or branched alkyl group having 12 to 18 carbon atoms) or tetrakis-[methylene-8-(3,5-di-t-glythyl-4-hydroxyphenylene/I/)propylene Phenolic antioxidant selected from onate comethane (hereinafter referred to as "antioxidant B")
A polypropylene resin sheet for thermoforming, characterized by being formed by extrusion molding a polypropylene resin composition containing 0.02 to 0.5 parts by weight, which solves the above conventional problems. The present invention will be explained in detail.

The polypropylene used in the present invention has a melt index (MI) of 0.1 to 109710 minutes, preferably 0.1 to 109710 minutes.
2 to 59710 minutes, a homopolymer of propylene,
A random copolymer with an α-olefin content of 10% by weight or less, a block copolymer with an ethylene content of 20% by weight or less, or a mixture thereof. Next, polyethylene has an MIo of 1 to 59710 minutes, preferably 0.2 to 89710 minute, and the density is 0.90-0
．． 97y7crA, low density polyethylene,
Medium-density polyethylene, high-density polyethylene, or a mixture thereof can be used depending on the purpose.The blending ratio of polypropylene is 70-100% by weight, preferably 30-95% by weight, based on the total amount of polypropylene and polyethylene.
It is t96.

If the amount of polypropylene blended is less than 70 times, it is unsuitable because the rigidity and 1# thermal properties of the resulting resin composition will decrease.

The blending ratio of polyethylene is 0 to 30% by weight, preferably 5 to 30% by weight based on the total amount of polypropylene and polyethylene.
Block copolymers are sometimes used alone in frozen food containers of 20 weight i5M in fields where low-temperature impact resistance is particularly required.

In the present invention, one or more antioxidants A selected from organic phosphite compounds, which are one of the essential components of antioxidants, include tris-(7-nogynolylphenyl/l/) phosphite. , distearyl-pentaerythritol-di-phosphite, 4,4'-butylidene-bis(8-methy/l/-6-t-butyl-phenyl-cytodecyl/l/) phosphite, tris(2°4- Examples include di-t-butylphenyl/l/) phosphite, particularly represented by the general formula (In the above formula, R3 represents the 8th butyl group or the 87th mil group.
4 represents a hydrogen atom, a methyl group, an 8th butyl M group, an 8th amino group, a phenyl group, or a cyclohexyμ group. R, represents a hydrogen atom, a methyl group or an 8-butyl ρ group; OR6 represents a hydrogen atom or a methyl group; However, R,, R, and R
All o's do not represent hydrogen atoms at the same time. ) Certain diaryl-pentaerythritol siphosphite compounds are preferred. Among them, bis(2,4-
Di-t-butylphenyl/L/) pentaerythritol y-
Shiftite is preferred.

The amount of antioxidant A added is 0.02 to 0 with respect to 100 parts by weight of the resin composition consisting of polypropylene and polyethylene.
．． 5 parts by weight, preferably 0.03 to 0.8 parts by weight. If the amount added is less than 0.02 part by weight, the effect of improving melt tension and flavor properties is small, and if it is more than 0.5 part by weight, the improvement effect reaches a plateau and new problems such as υ and bleeding occur.
Another essential ingredient for exerting the effects of the present invention is:
General formula (1) (where R1 is a methyl group or t-butyl group, R2 is
represents a straight chain or branched alkyl group having 12 to 18 carbon atoms. ) or tetofukisu[methylene-
A phenolic antioxidant (antioxidant B) selected from 8-(8,5-di-t-butyl-4-hydroxyphenylene/L/)propionate comethane, represented by the formula 〇(I) As a compound, octadecy/l/
-8-(8,5-di-t-butyne l/-4-hydroxyphenylene/L/)propionate, and lauryl-8-
(8,5-di-t-buty)Lt-4-hydroxypheny/I/)propionate is preferably used.

The amount of antioxidant B added is 0.02 to 0.5 parts, preferably 0.08 to 0 parts per 100 parts of the resin composition.
．． It is an 8-type filling part. If the amount added is less than 0.02 part by weight, the improvement effect of the present invention is small, and if it is more than 0.5 part by weight, the improvement effect reaches a plateau and new problems such as bleeding occur, which is inappropriate.

The polypropylene resin composition according to the present invention may contain amorphous ethylene-
A propylene copolymer, other resins, antioxidants, antistatic agents, lubricants, fillers, colorants, bactericidal agents, light stabilizers, etc. can be added as needed.

The polypropylene resin composition of the present invention is obtained by blending the above-mentioned components in an appropriate order and mixing by a conventional means such as an extruder, a Henschel mixer, or a Banbury mixer.
In particular, by using an extruder or the like, it is possible to produce molded products of specific shapes such as sheets and films. Further, a desired molded product can be obtained by directly molding the triblend using an extruder or the like.

The thickness of the polypropylene resin sheet for thermoforming of the present invention obtained as described above is 0.01 to 5 cm, preferably 0.
．． 1 to 3 IaI, this resin sheet can be used as a single layer or as a multilayer sheet with other resins, and can be used for vacuum forming, pressure forming, hot plate heating pressure forming, etc. 9. Secondary molding into food containers.

<Effects of the Invention> As described above, the present invention provides a polypropylene resin sheet for thermoforming which has excellent melt process tension and improved odor.

Therefore, the polypropylene resin sheet according to the present invention is useful for various uses due to the above-mentioned properties. It is used in the manufacture of containers and trays, and the food contents can be stored as is or after being subjected to treatments such as hot filling or heat sterilization, and the flavor properties of the food can be suitably maintained.

Examples> Hereinafter, the present invention will be described in more detail with reference to Examples. The measurement method used on each side is as follows◇ 1) Measurement of melt index (Ml) JIS K67
58, polypropylene was measured at 230°C and polyethylene at 190°C.
095m11, 6m long orifice, descending speed 5.7 w/min 1 winding speed 15.8 at 190℃
Measured in m/min.

8) Odor test An odor test of the sheet was conducted to evaluate flavor properties. Put 2Of samples cut from the sheet into the size of the bedding into a wide-mouthed glass bottle with a capacity of 250 mj, and add 60
After adjusting the state in an open air at ℃ for 30 minutes, the odor intensity in the gas phase was evaluated by 8 people on a 5-point scale. 01: Odor intensity
Weak 2: 〃 Slightly weak 8: 〃 Medium 4: ＃ Strong 5: 〃
Very strong example I MI 0. 85 parts by weight of polypropylene homopolymer of f3F/10 min and MI of 0.4' I/10 min (190°C
10QWiJLt parts of a resin composition consisting of 15 parts by weight of low-density polyethylene (calcium stearate) 0
．． 05 parts by weight as antioxidant A, 0.1 part by weight of bis(2,4-di-t-butylphenyl/L/)pentaerythritol shift nuphaite, and as antioxidant B stearyl/l/-8-( s, g-di-t-butyne l/-41
-Hydroxyphenylene/I/) propionate (0.10 parts by weight) was added, mixed in a Henschel mixer, and extruded at 230°C using a 65 φ extruder to form pellets. This pellet was extruded using a 65fiφ extruder equipped with a T die at a die temperature of 240°C, and the thickness was Q and the width was 2 mS.
A sheet of No. 251111 was prepared. Various physical properties of the obtained sheet were measured. The results are shown in Table 1.

Examples 2 and 3 The same results as in Example 1 were used except that the types of antioxidant A and antioxidant B were changed in Example 1.
Example 4 MI is 0.81710 minutes, ethylene content is 4.2 wt%
Table 1 shows the results obtained in the same manner as in Example 1 except that 100 parts of the block copolymer was used. The same procedure as in Example 1 was carried out except that 0.1 part by weight of 2,6-di-t-butyl-4-hydroxytoluene was added. The results are shown in Table 1. Example 2 Antioxidant A as, bis(2,4-di-butylphenyl)pentaerythritol sulfate) 0.2
The results were shown in Table 1 in the same manner as in Example 1, except that part by weight was added and antioxidant B was not added.

Claims (1)

[Claims] 70-100% by weight of polypropylene and 0-100% by weight of polyethylene
For 100 parts by weight of a resin composition consisting of 30% by weight, 0.02 to 0.5 parts by weight of one or more antioxidants selected from organic phosphite compounds and a compound of the general formula (
I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (However, R_1 is a methyl group or t-butyl group, R_
2 represents a straight chain or branched alkyl group having 12 to 18 carbon atoms. ) or tetrakis-[methylene-
A polypropylene resin composition containing 0.02 to 0.5 parts by weight of a phenolic antioxidant selected from 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane is extruded. A polypropylene resin sheet for thermoforming that is characterized by its ability to