JPH03179048A - Vinylidene chloride resin composition - Google Patents

Abstract

PURPOSE:To prepare the title compsn. having an improved thermal stability during molding and giving a molded article with improved oxygen barrier properties by compounding, as the main component, a copolymer comprising vinylidene chloride units and 2-ethylhexyl acrylate units in a specified ratio. CONSTITUTION:Vinylidene chloride and 2-ethylhexyl acrylate are copolymerized at 0-100 deg.C in the presence of an oil-sol. initiator comprising an org. peroxide having a 10hr half-life temp. (in 0.2mol/l benzene soln.) of 80 deg.C or lower and, if necessary, a suspending agent and a chain transfer agent, thus giving a copolymer comprising 90-93wt.% vinylidene chloride units and 7-10wt.% 2-ethylhexyl acrylate units. The title compsn. is obtd. by compounding the copolymer, if necessary, another vinylidene chloride resin, a thermal stabilizer comprising an epoxy compd., and, if necessary, an antioxidant, a thermal stabilizer aid, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a resin composition that can be molded into a bottom shape without adding a plasticizer, a molded body such as a pellet made from the resin composition, and a food product using the composition. It relates to use as packaging films, sheets and containers.

(Conventional technology) Vinylidene chloride resin has excellent oxygen barrier properties, moisture resistance, transparency, chemical resistance, oil resistance, adhesion, heat shrinkage, etc., and has high food hygiene properties, so it is Films formed by the inflation silane method and containers shaped by the conventional blow method are widely used for food packaging.

Conventionally, vinylidene chloride-vinyl chloride copolymer is commercially available as a vinylidene chloride-based resin used in this field, but this polymer has poor thermal stability during extrusion processing, so heat stabilizers are required. The base was made by blending an epoxy compound, a plasticizer such as dibutyl sebakey (DBS), acetyl tributyl citrate (ATBC), etc., which are liquid at room temperature, and an antioxidant, a heat stabilizing agent, etc.

However, at present, the environment is moving toward reducing the amount of plasticizers that have traditionally been used as much as possible from the viewpoint of food hygiene. The reason for this is that some of the plasticizer migrates to the food packaged in film or containers.

As a technique related to a vinylidene chloride resin composition that does not use a plasticizer, for example, Japanese Patent Publication No. 38-26569 has been proposed. This publication contains 70 to less than 90% by weight of vinylidene chloride monomer units, and acrylic acid esters of alcohols or phenols (however, the alcohol residues in the esters are long-chain aliphatic alkyls, fatty acids, etc. having 4 to 1 carbon atoms, Contains a cyclic alkyl or alkylaryl group, and the phenol residue in the ester has 6 carbon atoms.
A resin and [l acid product] formed by blending a small amount of stabilizer without using a plasticizer with a copolymer consisting of 5 to 30% by weight of monomer units (including ~18 benzene, alkylbenzene, and chlorobenzene) Processing is disclosed.

The characteristics of the technology described in this publication are that the amount of vinylidene chloride used is less than 90% by weight to improve thermal stability during extrusion processing, internal plasticization is achieved by copolymerizing acrylic acid ester of alcohol or phenol, The crystallization rate is increased to improve moldability. It is known that the crystallization rate increases as the number of vinylidene chloride monomer units in the copolymer increases, but Japanese Patent Publication No. 3B-26569
In the resin composition described in the publication, the vinylidene chloride monomer unit is less than 90% by weight, so the oxygen barrier property is poor, and the crystallization rate is not sufficient, so the bubbles do not expand in the machine direction during inflation processing and do not expand in the transverse direction. It expands and is extremely difficult to mold, and if the mold is not cooled down enough to promote crystallization when manufacturing containers by blow molding, the original shape of the container will be destroyed and deformed, resulting in poor molding cycles. There was a drawback.

(Problems to be Solved by the Invention) The present invention has excellent thermal stability during molding even without the use of plasticizers, and enables inflation method film formation, blow molding, granulation molding, and especially melt extrusion pelletization. The object of the present invention is to obtain a resin & IItc material having a high degree of crystallinity and having an excellent oxygen barrier property of the resulting molded product.

(Means for solving the problem) In general, the internal plasticizing ability of acrylic esters decreases as the number of carbon atoms in the alcohol residue in the ester increases, and this can be estimated from the glass transition temperature of the homopolymer. .

The present inventor attempted to copolymerize acrylic acid 2-ethylhexyl ester (the number of carbon atoms in the alcohol residue is 8) with vinylidene chloride, which has the lowest glass transition temperature among acrylic acid ester homopolymers, and as a result of intensive study. The present invention was achieved by discovering that a vinylidene chloride resin composition can be obtained which has sufficient internal plasticizing ability and crystallization rate during processing and has excellent thermal stability.

That is, the present invention includes: 90 to 93% by weight of vinylidene chloride monomer units;
It is characterized by a resin composition containing a copolymer containing 7 to 10% by weight of acrylic acid 2-ethylhexyl ester monomer unit.

Furthermore, in the present invention, it is a preferred embodiment that an epoxy compound is blended into the resin composition as a heat stabilizer.

Furthermore, the present invention will be specifically explained.

The copolymer constituting the resin composition of the present invention can generally be produced by a suspension polymerization method using an oil-soluble initiator and a suspending agent or an emulsion polymerization method using a water-soluble initiator and an emulsifier.
Without being limited thereto, any polymerization method used to produce vinylidene chloride resins can be applied. However, it is preferable to use a suspension polymerization method that does not require a salting-out step after polymerization.

Suspension polymerization methods include the direct suspension method in which nanatsumer is added to water in which a suspending agent is dissolved, or the method disclosed in Japanese Patent Application Laid-Open No. 62-2802.
As described in Publication No. 07, water in which a suspending agent is dissolved is added to the monomer to create a dispersed state in which the monomer phase is a continuous phase and water is a discontinuous phase, and the monomer is discontinuous/water is a discontinuous phase. Any suspension method in which a dispersion is formed as a continuous phase may be used.

The oil-soluble initiator used to produce the copolymer of the present invention is 0.2 mol/j! in a benzene solution. Organic peroxides whose half-life is 10 hours at a concentration of 80°C or less, the so-called decomposition temperature, such as diacyl peroxide-based imbutyl peroxide, 2,4-dichlorobenzoyl peroxide, orthomethylbenzoyl peroxide, bis-3,5,5-)limethylhexanol peroxide, acetyl peroxide, benzoyl peroxide, parachlorobenzoyl peroxide, alkyl perester acetylcyclohexane sulfonyl peroxide, 2,4,4-trimethyl Pentyl peroxyphenoxy acetate, t-
Butylperoxyneodecanoate, L-butylperoxypivalate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate,
Percarbonate-based di-3-methoxybutyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, bis(1-t-butylcyclohexyl) peroxydicarbonate, diisopropyl peroxydicarbonate, di-5ec-butylperoxydicarbonate One or more types can be selected from carbonate, t-butylperoxyisobrobyl carbonate, and azobis compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile. The amount used is not critical to the invention;
It is sufficient to use an amount that will result in a copolymer having the desired molecular weight.

The suspending agent used to produce the copolymer of the present invention has a viscosity of 1 (1 to 30,
0OOcps of cellulose derivatives, such as methylcellulose, ethylcellulose, cellulose acetate, cellulose acetate butyrate, carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, ethylhydroxyethylcellulose, and partial saccharides of polyvinyl alcohol and polyvinyl acetate. One or more types can be selected from compounds, etc. The amount used is preferably 0.03 parts by weight or more per 100 parts by weight of the monomer. If the amount is less than this amount, suspension stability may deteriorate and particles may adhere to each other during polymerization to form lumps.

Furthermore, in order to produce the copolymer of the present invention, a chain transfer agent such as trichlorethylene, dodecyl mercaptan, octyl mercaptan, etc. may be added and mixed during polymerization, if necessary.

In producing the copolymer of the present invention, the polymerization temperature is not particularly limited, but is generally 0 to 100°C, preferably 55 to 100°C.
80°C is suitable.

After the above polymerization is completed, filtration, washing with water, and drying are performed as necessary, but in the case of emulsions, salting out with aluminum sulfate, Glauber's salt, etc. is performed, and then the usual post-treatment is performed to obtain powdered or granular resin. be able to.

The copolymer resin thus obtained may be subjected to the next molding process as it is, but a heat stabilizer as described later, a light stabilizer, a coloring agent, etc. may be added in advance during the polymerization or during the polymerization. It may be added later if necessary.

The copolymer composed of the resin & II compound acid of the present invention essentially contains 90 to 93% by weight of vinylidene chloride monomer units.
, 7 to 10% by weight of acrylic f112-ethylhexyl ester monomer.

As long as this requirement is met, there is no problem in copolymerizing one or more other vinyl monomers such as vinyl chloride, acrylonitrile, methacrylnitrile, vinyl acetate, etc. in a small amount, for example, 10% by weight or less.

If the vinylidene chloride monomer unit in the copolymer used in the present invention is less than 90% by weight, the crystallization rate required for molding will not be sufficient, and if it exceeds 93% by weight, thermal stability during molding will be insufficient. It is undesirable because it makes your sex worse.

The molecular weight of the copolymer used in the resin composition of the present invention is not particularly limited, but may be within the range of the molecular weight of ordinary bottom grade vinylidene chloride resins, for example from about 70,000 to about 150,000. can use things.

As the resin component constituting the resin composition of the present invention, the above-mentioned specific copolymer may be used alone, or the copolymer may be the main component, and a small amount of other vinylidene chloride resin may be included as long as the function is not impaired. You can let me.

Epoxy compounds that can be suitably added to the resin composition of the present invention include, for example, epoxidized vegetable oil-based epoxidized soybean oil,
One or more types can be selected from epoxidized linseed oil, epoxidized amberjack oil, epoxy resin-based bisphenol A diglycidyl ether, epoxidized polybutadiene, epoxidized monoester-based epoxidized octyl stearate, and the like.

The blending amount is 1 to 2 per 100 parts by weight of the copolymer.
．． The amount is preferably 5 parts by weight, and if it is less than 1 part by weight, sufficient thermal stability will not be achieved, and if it exceeds 2.5 parts by weight, the oxygen barrier property, which is a characteristic of vinylidene chloride resin compositions, will be impaired.

In addition, to further improve thermal stability, antioxidants, thiodipropionic acid alkyl esters, and metal oxide-based thermal stabilization aids that are conventionally used in vinylidene chloride resins may be added. .

Examples of antioxidants are vitamin E, BHT.

BHA, etc., but preferably vitamin E, which has high food stability.

Examples of thermal stabilizing aids include sodium pyrophosphate and sodium tripolyphosphate for phosphate salts; EDTA.2Na for EDTA salts; dilauryl thiodipropionate and thiodipropionic acid for alkyl thiodipropionate esters. Distearyl: Among metal oxide systems, magnesium oxide (MgO) is preferred.

Furthermore, the resin composition of the present invention may contain various additives, such as light stabilizers, colorants, lubricants, etc., within a range that does not impair the properties of the specific copolymer of the present invention.

The resin composition of the present invention may be subjected to molding in the form of copolymer powder as obtained by copolymerization or in the form of granules, but it may also be used as pellets preformed with a granulator such as a pelletizer. It is preferable to form a preformed body of 1. By making such a preformed body, it does not aggregate in the hopper during melt molding, for example, extrusion molding, unlike conventional powder forms, and has good moldability. Very good.

Furthermore, the resin composition of the present invention can be used to form various molded products such as films and sheets by molding methods known per se, such as injection molding, extrusion molding, extrusion blowing, and inflation methods, and various molded products, especially food packaging films. , can be formed into sheets, containers, etc.

As described above, the resin composition of the present invention can be easily molded without adding a plasticizer, has excellent thermal stability during molding, and has a fast crystallization rate, so it is particularly suitable for food packaging films, sheets, and containers. Since it can be produced in a continuous process and has excellent oxygen barrier properties, it is extremely useful as a molding material for food packaging films, sheets, containers, etc.

Next, the present invention will be explained in detail using Examples and Comparative Examples, but these do not limit the scope of the present invention.

Thermal stability, crystallization rate, film formation test by inflation method, container molding test by blow method, pelletization test, oxygen barrier property, and molecular weight in the examples were conducted using the following methods.

(i) Thermal stability: While kneading the vinylidene chloride resin composition at 170"C and 50 rpm using a Brabender Plastograph, the molten resin composition was sampled every 2.5 minutes. The discoloration over time was observed, and the thermal stability during extrusion processing was evaluated based on the degree of discoloration.The evaluation results were expressed by the following symbols.

O: Excellent (level without any problem in practical molding process) O: Good (level without problem in practical molding process) Δ: Fair (
(Level that causes some problems in practical bottom shape processing)
After drying at °C for 1 minute and heat treatment at 220 °C for 30 seconds, immediately immerse in cold water at 4 °C.Next, remove from cold water and immediately peel off the copolymer film from the Teflon sheet.゜200 CI-'~800 cta
-' IR spectrum is taken.

At this time, it is confirmed that there is no absorption of 1.046C11-'. Thereafter, the copolymer film is left in an atmosphere at 20° C., and an IR spectrum is taken every time (arbitrarily).

Calculation of relative crystallinity (%) is 1.100 cm-' and 85
Connect a line using 0CI-' as a target and calculate the absorbance ratio at 1,070 cm-' and 1,046 cm-' from this line. A) IR spectrum of a copolymer film separately heat-treated at 95°C for 30 minutes. In the same manner, the absorbance ratio was calculated as B), (A/B) x 10o.

(iii) Film formation test by inflation method: Extruded ml (40 m + φ, L/D = 21
) to melt resin Allll hardware 80-185'C, circular die 3 (27msφ, slit 1.1mm)
Mineral oil was injected as an anti-blocking agent into the tubular resin composition (hereinafter referred to as parison) 11 which was extruded at 12 kg/hr from 12 kg/hr, and the mixture was passed through a cooling bath 4 at 7°C and a preheating bath 5 at 60″C. After that, the parison temperature is 52℃ and air is introduced to create an inflation bubble (unstretched film) 6.
The resulting tubular stretched film 7 was wound up. At this time, film formability was evaluated based on the time required for continuous winding.

(iv) Container molding test using blow method: Extruder and circular used for bottom membrane test using inflation method
A mold 9 in which the resin composition was melted at 180 to 185°C and the extruded parison was kept at 50 to 60°C using a die.
(shown in Figure 2), molded by blowing compressed air, and removed from the mold after 5 seconds and placed in a 20'C atmosphere for 1 hour.
The container was left to stand for 0 minutes and the deformation of the container was examined.

(v) Pelletization test: The resin composition was melted at 180-185°C using the extruder shown in Fig. 1 and pellet die 3 (15Wφ) used for the bottom film test by the inflation method, and
After passing through a cooling bath at 7°C, the cylindrical resin extruded at
It was passed through a cooling bath at ~14°C and cut with a pelletizer. At this time, the strand temperature immediately before cutting was 45°C.

(vi) Oxygen barrier property: A film with a thickness of 25 μm was obtained by extrusion of resin and strong acid, and the oxygen permeability 1 of this film was determined by AsTM-D3985.
To! It was measured based on # and converted into a value of 1μ thickness (unit:
CC・μm/nf・24Hr・atm-at20'c,
, 100%RH).

(vi) Molecular weight: The molecular weight was measured by gel permeation chromatography using polystyrene as a standard.

(Example 1) 120 parts of deionized water in which 0.2 parts of hydroxypropyl methylcellulose was dissolved was put into a reactor equipped with a stirrer and the interior was glass lined, and after purging the system with nitrogen at 30°C, vinylidene chloride was added. Monomer (hereinafter abbreviated as VDC) 9
A mixture of 2.5 parts by weight of acrylic acid 2-ethylhexyl ester (hereinafter abbreviated as 2HA), and 0.9 parts by weight of (-butylperoxy 2-ethylhexanoate) was introduced into the reactor. Polymerization is started by raising the temperature to 75°C. After 10 hours, the temperature inside the reactor is lowered to 30°C and the slurry is taken out. The resulting slurry is separated from water using a centrifugal dehydrator, and then VDC/2EHA copolymer 99 in granule form after drying for 24 hours in a hot air dryer
Parts by weight were obtained.

The molecular weight of this copolymer was determined to be 87.90 by gel permini-silane chromatography using polystyrene as a standard.
It was 0.

Next, to 100 parts by weight of the obtained copolymer, 2.0 parts by weight of bisphenol A diglycidyl ether, 0.01 parts by weight of vitamin E, 0.02 parts by weight of EDTA/2Na, and 0.4 parts by weight of MgO. Thermal stability was evaluated by blending parts by weight.

Example 2 The crystallization rate of the copolymer obtained in Example 1 was measured, and 2.0 parts by weight of bisphenol A diglycidyl ether and 0.01 part of Vitayon E were added to 100 parts by weight of the copolymer.
parts by weight, and 0.02 parts by weight of EDTA/2Na were blended, and evaluation of thermal stability, extrusion film formation test by inflation method and measurement of oxygen permeation amount, container molding test and pelletization test by blow method were carried out.

Example 3 Nine parts by weight of a copolymer were obtained in the same manner as in Example 1, except that 90 parts by weight of VDC and 10 parts by weight of 2EHA were used.

The molecular weight of the obtained copolymer was 87,100.
Next, the same evaluation as in Example 2 was performed.

Comparative Example 1 99 parts by weight of the copolymer was prepared in the same manner as in Example 1, except that 95 parts by weight of VDC, 5 parts by weight of 2EHA, and 0.775 parts by weight of -butylperoxy 2-ethylhexanoate were used. I got it.

The resulting copolymer had a molecular weight of 86,100.Next, a stabilizer was added in the same manner as in Example 1 to evaluate thermal stability.

Comparative Example 2 99 parts by weight of a copolymer was obtained in the same manner as in Example 1, except that VDC was changed to 87.5 parts by weight and 2EHA was changed to 12.5 parts by weight.

The obtained copolymer had a molecular weight of 93.000. Next, the same evaluation as in Example 2 was carried out.

Comparative Example 3 An attempt was made to obtain a polymer in the same manner as in Example 1 except that 80 parts by weight of VDC and 20 parts by weight of 2EHA were used, but the copolymer particles adhered to each other during centrifugal dehydration, resulting in a granular shape. It didn't happen.

Comparative Example 4 81.5 parts by weight of VDC, 18.5 parts by weight of vinyl chloride (hereinafter abbreviated as VC), 0.2 parts by weight of diisopropyl peroxydicarbonate, and the temperature inside the reactor was set to 45°C.
90 parts by weight of a copolymer was obtained in the same manner as in Example 1, except that the temperature was lowered after 0 hours.

The obtained copolymer had a molecular weight of 92,500.Next, a stabilizer similar to that in Example 2 was blended, and thermal stability evaluation and a film formation test by an inflation method were conducted.

Comparative Example 5 The same stabilizer as in Example 2 and 5 parts by weight of ATBC as a plasticizer were added to the copolymer of Comparative Example 4, and evaluation of thermal stability, crystallization rate measurement, and formation by the inflation method were carried out. Membrane tests, oxygen permeation measurements, container molding tests using the blow method, and pelletizing tests were conducted.

The above evaluation results are shown in Table-1.

As shown in Table 1, when the VDC monomer unit in the copolymer exceeds 93% by weight of the present invention, thermal stability is poor and resin decomposition products (carbon) are generated during film formation by the inflation method, resulting in bubble rupture. Continuous film formation for 10 minutes or more was impossible.

Furthermore, if the amount of VDC heptad units in the copolymer is less than 90% by weight of the present invention, the crystallization rate will be slow, and bubbles will burst in the transverse direction during film formation by the inflation method. Continuous film formation is not possible,
Deformation of the molded container by blowing also occurred within 10 minutes, and in extrusion pelletization the strands did not become hard and could not be cut.

As described above, since the resin composition of the present invention uses a specific VDC monomer-containing copolymer as the main constituent resin, the crystallization rate is, for example, 500 seconds or less, preferably 150 seconds or less.
It is suitable for high-speed continuous molding because it can be molded into molded products with excellent oxygen barrier properties and thermal stability in less than a second.

(Effects of the Invention) The resin composition of the present invention does not contain a plasticizer, has excellent thermal stability during processing, and has a fast crystallization rate. Not only has it become easier to make sheets using the casting method and containers using the blowing method, but the oxygen barrier properties have also been further improved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an outline of the flow used in a film formation test using the inflation method of the resin composition of the present invention. Fig. 2 is a schematic diagram showing the outline of the mold used for the container bottom shape test by the blowing method of the resin and acid of the present invention. Preheat bath 6: Unstretched film: Stretched film: Winding: Bottle mold: Accumulation head: Parison

Claims (1)

[Claims] 90-93% by weight vinylidene chloride monomer unit
, a vinylidene chloride resin composition comprising a copolymer containing 7 to 10% by weight of acrylic acid 2-ethylhexyl ester monomer unit.