JP3105901B2 - Resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a melt extrudable polyvinyl alcohol-based copolymer resin composition having an excellent oxygen barrier property.

More specifically, it relates to a polyvinyl alcohol-based copolymer resin composition obtained by mixing a polyvinyl alcohol-based copolymer emulsion obtained by emulsion polymerization of vinyl acetate and ethylene in the presence of polyvinyl alcohol and a polyvinyl alcohol aqueous solution.

[Prior Art] It has been a long time since a functional packaging material having a gas barrier for preventing food from being decomposed by oxygen or water vapor has been developed.

These include polyvinylidene chloride, ethylene-vinyl alcohol copolymers, polyethylene terephthalate, polyacrylonitrile copolymers, etc., either alone or laminated with another resin, as a gas barrier film, container, coating material. Widely used.

Among these, ethylene-vinyl alcohol copolymer is a resin having a high oxygen barrier property next to polyvinyl alcohol resin under low humidity, and also has a better gas barrier property than polyvinyl alcohol resin under high humidity, and Since it is easy to melt-extrude, it is widely used for packaging materials that require oxygen barrier properties.

This ethylene-vinyl alcohol copolymer is usually obtained by saponifying a solution-polymerized ethylene-vinyl acetate copolymer, followed by washing and drying. Therefore, there are many problems such as a large loss during the filtration operation of the polymer after the saponification reaction, a large amount of energy is required to recover the solvent used for the polymerization, and complicated equipment must be installed. It was

In recent years, polyvinyl alcohol/vinyl acetate/ethylene copolymers (Japanese Unexamined Patent Publication No. Sho 60-96637) and modified polyvinyl alcohol (Japanese Unexamined Patent Publication No. Sho 63-108016), which are resins having an oxygen barrier property even if the saponification step is omitted, Is proposed.

[Problems to be Solved by the Invention] However, the polyvinyl alcohol/vinyl acetate/ethylene copolymer disclosed in JP-A-60-96637 discloses a polyvinyl alcohol in a reaction solution during emulsion polymerization in order to obtain an oxygen barrier property. It requires a concentration of 15% by weight or more. Therefore, this copolymer has a problem that the emulsion viscosity is extremely high and it is difficult to remove heat during polymerization. In order to lower the emulsion viscosity, there are restrictions such as the need to lower the solid content of the emulsion, which is not an economical method.

Also, the invention disclosed in Japanese Patent Laid-Open No. 63-108016 has a restriction that the solid content concentration (nonvolatile content) must be lowered for the same reason as above.

Generally, when emulsion copolymerization of vinyl acetate and ethylene is performed in the presence of a solution having a polyvinyl alcohol concentration of 15% by weight or more based on the total amount of polyvinyl alcohol and vinyl acetate monomers, when the polymer concentration becomes a high concentration of 50% or more. Viscosity increases to 30,000 cps or higher. When the viscosity is above 30,000 cps, it becomes difficult to remove the reaction heat,
It is economically disadvantageous to control the polymerization by cooling ordinary cooling water and to require special cooling auxiliary equipment.

Therefore, in order to obtain a polyvinyl alcohol-based copolymer emulsion in which the polymerization can be controlled, the solid content concentration must be lowered and/or the polymerization rate must be extremely slowed down to suppress the heat generation amount of the polymerization reaction, and to perform the polymerization operation for a long time. I have to. Therefore, there is a problem that the manufacturing efficiency is extremely lowered.

In particular, when the amount of polyvinyl alcohol is 15% by weight or more, these are further restricted.

[Means for Solving the Problems] As a result of intensive studies conducted by the present inventors to improve the restrictions caused by heat removal during the production of the gas barrier resin, (A) polyvinyl alcohol and vinyl acetate Based on the total amount of monomers, polyvinyl alcohol is 10 to
Polyvinyl alcohol emulsion of ethylene-vinyl acetate copolymer having an ethylene content of 1 to 50% by weight with respect to vinyl acetate, obtained by emulsion polymerization of vinyl acetate monomer and ethylene in the presence of 15% by weight, and (B) emulsion Oxygen characterized by being mixed with other polyvinyl alcohol in an aqueous solution so that the total amount of polyvinyl alcohol units contained in the resin composition is at least 15% by weight with respect to the total amount of vinyl alcohol units and vinyl acetate units. A barrier emulsion resin composition is provided.

Also, an oxygen barrier resin composition comprising the above (A) polyvinyl alcohol-based copolymer emulsion and (B) polyvinyl alcohol mixed to form an emulsion resin composition, and then the resin solid component is separated. To do.

As described in detail below, this resin composition is an excellent resin composition that does not have the problem of heat removal in the above reaction, can be stably produced, and has both high oxygen barrier properties and melt extrusion moldability.

That is, in an emulsion having a high solid content concentration which is economical in production, 10 to 15% by weight of polyvinyl alcohol is added to the total amount of polyvinyl alcohol and vinyl acetate so as to form a low-viscosity emulsion which is easy to remove heat by polymerization. The copolymer emulsion obtained by emulsion polymerization of vinyl acetate and ethylene in the presence of a solid content concentration of 20% by weight or more and polyvinyl alcohol in an aqueous solution are mixed, and the polyvinyl alcohol in the emulsion resin composition and In the present invention, a resin composition having a high oxygen barrier property and a high melt extrusion moldability was found by forming a resin composition having a total amount of polyvinyl alcohol groups of at least 15% by weight based on the total amount of vinyl alcohol units and vinyl acetate units. I arrived. In the present invention, since the amount of polyvinyl alcohol during emulsion polymerization is small, there are few restrictions in removing the heat of reaction described above, and it is possible to produce an emulsion concentration up to a high concentration. It can have barrier properties.

Polyvinyl alcohol used in the production of this emulsion polymerization is obtained by saponifying polyvinyl acetate, preferably 70-99% saponification degree, 100-3,000 degree of polymerization, particularly preferably 78-99% saponification degree, The degree of polymerization is 300 to 2,500.

The higher the saponification degree of polyvinyl alcohol, the better the oxygen barrier property, but the higher the viscosity of the liquid during polymerization,
The compatibility may be poor when the emulsion polymer and the polyvinyl alcohol aqueous solution are mixed. Therefore, a 78-99% partially saponified product is preferable.

The higher the degree of polymerization of polyvinyl alcohol used for emulsion polymerization, the higher the strength of the resin product obtained from the resin composition, but the worse the melt extrusion moldability. Therefore,
For this purpose, it is preferable to select and use polyvinyl alcohol having a degree of polymerization of 300 to 2,500, particularly preferably 300 to 1,500.

Further, in the preparation of the polyvinyl alcohol aqueous solution to be mixed with the polyvinyl alcohol-based copolymer emulsion, it is possible to dissolve without generating heat of dissolution, so that it is not necessary to remove heat.

Further, since there is no problem of removing the heat of reaction, the amount of polyvinyl alcohol and the degree of polymerization of polyvinyl alcohol can be selected according to the required performance in the preparation of the polyvinyl alcohol solution as compared with the aqueous solution for emulsion.

In any case, the concentration of the polyvinyl alcohol used in the emulsion polymerization and the polyvinyl alcohol aqueous solution cannot be determined because the polymerization degree and saponification degree of the polyvinyl alcohol affect the viscosity of the aqueous solution.

Emulsion polymerization of ethylene and vinyl acetate is carried out by enclosing ethylene and increasing the pressure. The pressure is usually 5 to 100 Kg/cm ² .

The ethylene, vinyl acetate, and ethylene contents in the emulsion can be varied within a relatively wide range by adjusting the ethylene pressure during polymerization.

The ethylene content must be in the range of 1% to 50% by weight with respect to vinyl acetate. Particularly preferably, the range is 5% by weight to 45% by weight. Ethylene content is 1% by weight
Below, the melt extrusion moldability is poor. On the other hand, if it is 50% by weight or more, the compatibility with polyvinyl alcohol is poor, which is not preferable.

The polyvinyl alcohol-based copolymer emulsion of the present invention may be further copolymerized with vinyl acetate and another monomer copolymerizable with ethylene.

Examples of vinyl monomers that can be used include vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl laurate, vinyl versatate, and other vinyl esters, vinyl chloride, vinyl fluoride, and other halogenated vinyls, and unsaturated compounds. Ethyl acrylate having 2 to 12 carbon atoms in the alkyl group represented by carboxylic acid alkyl ester,
(Meth)acrylic acid esters such as butyl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate,
Acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid and the like α. β-unsaturated carboxylic acid,
Unsaturated carboxylic acid amides such as acrylamide, methacrylamide, N-methylol acrylamide, and functional group monomers such as styrene, acrylonitrile or 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate can be used in combination.

As the polymerization catalyst, a persulfate usually used in emulsion polymerization,
A redox system with hydrogen peroxide, t-butyl hydroperoxide or a reducing agent is used.

If necessary, a surfactant can be used in combination.

[Operation] A resin composition of the present invention obtained by mixing a polyvinyl alcohol-based copolymer emulsion obtained by emulsion polymerization of vinyl acetate and ethylene in an aqueous polyvinyl alcohol solution and an aqueous polyvinyl alcohol copolymer is an oxygen barrier. The reason for the excellent properties and excellent melt extrusion moldability is not clear, but during fusion drying and melt molding between the interface between polyvinyl alcohol and ethylene-vinyl acetate copolymer resin, ethylene and vinyl acetate grafted polyvinyl alcohol It is presumed that compatibilization has occurred.

If the estimated ethylene/vinyl acetate grafted polyvinyl alcohol is present, the oxygen barrier property does not decrease even when the polyvinyl alcohol aqueous solution is mixed, but rather improves, and the melt moldability shows a value within the practical range. I think that the.

Further, the emulsion resin composition obtained by mixing the polyvinyl alcohol copolymer emulsion of the present invention and the aqueous solution of polyvinyl alcohol can be used as it is as a base of a coating material for emulsion coating, and when applied and dried, it is a transparent airtight film having an oxygen barrier property. Since it can be formed, it can also be used as a treating agent for imparting an oxygen barrier property to synthetic resin films, papers, cloths and the like.

Hereinafter, the present invention will be described with reference to examples.

[Example] The ethylene content of the resin was determined by the alkali saponification method.

[Measurement of oxygen permeation amount and melt extrusion molding method MFR]

Using a press molding machine at a temperature of 230 ℃ the resin composition,
A film with a thickness of 100 μm was created, and using this modern film (OXTRAN-10/50A) manufactured by Modern Control Co., measurement of oxygen permeation amount at a temperature of 23° C. and humidity of 65 RH% and JI
The MFR was measured according to S-K6758.

(Examples 1 to 3) [Preparation of polyvinyl alcohol-based copolymer emulsion] Stirrer, several supply ports, cooling and heating device, pressure gauge,
In a 30 liter autoclave equipped with a thermometer, polyvinyl alcohol GL-03 (polymerization degree 300, saponification degree 88%, manufactured by Nippon Synthetic Chemical Industry) 700 g and GL-05 (polymerization degree 500, saponification degree 88
%, manufactured by Nippon Gohsei Co., Ltd.), 700 g of polyvinyl alcohol aqueous solution dissolved in 5,600 g of water, 400 g of aqueous solution of 20 g of sodium acetate dissolved therein, and further charged with 8,600 g of vinyl acetate, applied with ethylene pressure of 5 Kg/cm ^2. The operation of returning to normal pressure was repeated twice to replace ethylene. Then, the ethylene pressure was maintained at 50 kg/cm ^2, and 2,000 g of a 2 wt% aqueous solution of ammonium persulfate as a catalyst and 2,000 g of a 5 wt% aqueous solution of sodium metabisulfite were uniformly added over 5 hours to carry out the reaction. .. During this period, the reaction temperature was kept at 60° C. for polymerization. Thereafter, the mixture was kept at 80° C. for further 2 hours for aging.

As a result, a polyvinyl alcohol/vinyl acetate/ethylene copolymer emulsion having a solid content concentration of 54.78% by weight and a viscosity of 8,000 cps was obtained.

[Preparation of polyvinyl alcohol aqueous solution]

Polyvinyl alcohol GL-03 was heated and dissolved in water at 70°C to obtain a 30% by weight aqueous solution of 2,700 cps at 23°C, which was mixed in a required amount.

[Mixing of polyvinyl alcohol copolymer emulsion and polyvinyl alcohol aqueous solution]

The polyvinyl alcohol-based copolymer emulsion prepared above was mixed by changing the ratio of the polyvinyl alcohol aqueous solution, and the mixed emulsion was left standing at -20°C for 20 hours to freeze-precipitate the resin, which was then freeze-pulverized and freeze-dried. At 80℃
After vacuum drying for 24 hours, the resins shown in Table 1 were obtained.

(Example 4) Polyvinyl alcohol PVA117 (polymerization degree 1,
An aqueous solution of 700, saponification degree 98.5%, manufactured by Kuraray Co., Ltd.
Similarly to the above, the total amount of polyvinyl alcohol in the emulsion resin composition was 50% by weight based on the total amount of polyvinyl alcohol and vinyl acetate, and the mixture was mixed in the same manner as in Example 1 to obtain a resin composition. ..

(Example 5) Polyvinyl alcohol GM-14L (polymerization degree 1,400, saponification degree 88%, was added to the 30-liter autoclave used in Example 1).
An aqueous solution prepared by dissolving 1,400 g of water in Japan (6,100 g)
After charging 2,620 g of an aqueous solution in which 500 g and 20 g of sodium acetate were dissolved, ethylene of 5 kg/cm ² pressure was applied in the same manner as in Example 1,
The operation of maintaining normal pressure was repeated twice to replace ethylene. Furthermore, the ethylene pressure was maintained at 50 kg/cm ² during the reaction, and then 8,600 g of vinyl acetate and 1.500 g of a 2% aqueous solution of ammonium persulfate as a catalyst and 1,500 g of a 5% aqueous solution of sodium metabisulfite.
Was added uniformly over 5 hours. During this period, the temperature was kept at 70° C. for polymerization. Then, the mixture was kept at 80° C. for 2 hours for aging.

A polyvinyl alcohol/vinyl acetate/ethylene copolymer emulsion having a solid content concentration of 44.93% by weight and a viscosity of 28,000 cps was obtained.

This emulsion and the polyvinyl alcohol aqueous solution used in Examples 1 to 3 were mixed and treated in the same manner as in Example 2 to obtain a resin composition.

Table 2 shows the measurement results of MFR, which is an index of the amount of oxygen permeation and melt extrusion moldability.

(Example 6) The polyvinyl alcohols of Examples 1 to 3 were mixed with GL-03 and GL-
The procedure of Example 1 was repeated, except that the mixture of 05 was changed to only GL-05, and the amount was changed to 1,000 g and the amount of vinyl acetate was changed to 9,000 g.

A polyvinyl alcohol copolymer emulsion having a concentration of 54.82% and a viscosity of 8,500 cps was obtained.

This emulsion and the aqueous polyvinyl alcohol solution used in Examples 1 to 3 were mixed and treated so that the total amount of polyvinyl alcohol in the emulsion resin composition was 15% by weight with respect to the total amount of polyvinyl alcohol and vinyl acetate. I got a thing.

Table 2 shows the measurement results of MFR, which is an index of the amount of oxygen permeation and melt extrusion moldability.

(Example 7) 5,040 g of polyvinyl alcohol GL-03 280 g and GL-05 280 g were added to the 30-liter autoclave used in Example 1.
5,600 g of an aqueous solution in which water was dissolved and 6,960 g of an aqueous solution in which 20 g of sodium acetate were dissolved were charged, and ethylene at a pressure of 5 kg/cm ² was applied in the same manner as in Example 1, and this operation was repeated twice to replace ethylene. Furthermore, the reaction was carried out while maintaining the ethylene pressure at 50 Kg/cm ² . Next, 3,440 g of vinyl acetate, 2,000 g of a 2 wt% aqueous solution of ammonium persulfate as a catalyst, and 2,000 g of a 5 wt% aqueous solution of sodium metabisulfite were uniformly added over 5 hours. During this time, the temperature is kept at 60° C. to polymerize. Then, the mixture was kept at 80° C. for 2 hours for aging.

A polyvinyl alcohol emulsion having a solid content concentration of 24.07% by weight and a viscosity of 200 cps was obtained. In this emulsion,
As in Example 2, the aqueous polyvinyl alcohol solution used in Example 1 was added and mixed so that the total amount of polyvinyl alcohol in the emulsion resin composition was 50% by weight based on the total amount of polyvinyl alcohol and vinyl acetate. A resin composition was obtained in the same manner as in Example 2 except for the above, and the same measurement was performed.

(Comparative Example 1) 5,000 g of an aqueous solution prepared by dissolving 500 g of polyvinyl alcohol GL-05 in the 30-liter autoclave used in Example 1.
Then, 1,500 g of an aqueous solution in which 20 g of sodium acetate was dissolved was charged, and ethylene substitution was carried out in the same manner as in Example 1. Then change the ethylene pressure to 50
While maintaining at kg/cm ² , 9,500 g of vinyl acetate, 2,000 g of a 2 wt% aqueous solution of ammonium persulfate as a catalyst, and 2,000 g of a 5 wt% aqueous solution of sodium metabisulfite were uniformly added for 5 hours to carry out the reaction. .. During this time, the temperature is kept at 60° C. to polymerize. Then, the mixture was kept at 80° C. for 2 hours for aging.

A polyvinyl alcohol/vinyl acetate/ethylene copolymer emulsion having a solid content concentration of 54.60% by weight and a viscosity of 2,300 cps was obtained. In this emulsion, as in Example 1, the total amount of polyvinyl alcohol in the emulsion resin composition was relative to the total amount of polyvinyl alcohol and vinyl acetate.
The polyvinyl alcohol aqueous solution used in Example 1 was added and mixed so as to be 10% by weight, and the other measurements were performed in the same manner as in Example 1.

(Comparative Example 2) Polyvinyl alcohol GL-03 and GL- used in Example 1
GH-17 (Polymerization degree 1,700, Saponification degree 8
8%, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was carried out in the same manner as in Example 1, except that vinyl acetate, a catalyst ammonium persulfate and an aqueous solution of sodium metabisulfite were uniformly added so as to be completed in 5 hours. At the beginning of the 3rd hour, temperature control became impossible due to the high viscosity, and the reaction was stopped.

(Comparative Example 3) Polyvinyl alcohol GL-03 and GL- used in Example 1
In place of the mixture with 05, GM-14L 2,500 g was dissolved in water 5,800 g polyvinyl alcohol aqueous solution 8,300 g and sodium acetate 20 g aqueous solution 200 g was charged, and after ethylene substitution, ethylene pressure was changed to 50 Kg/cm ² . The reaction was carried out while holding. Next, 7,500 g of vinyl acetate, 500 g of an 8 wt% aqueous solution of ammonium persulfate as a catalyst, and sodium metabisulfite.
An attempt was made to uniformly add 1,000 g of a 10% by weight aqueous solution in 5 hours, but at 3.5 hours after the uniform addition was started, temperature control became impossible due to high viscosity.

(Example 8) The emulsion resin composition obtained in Example 1 was prepared to a thickness of 50 μm.
20 m thick on m polyester film (Du Pont)
It was applied so as to have a thickness of μm and dried at room temperature for 1 week. Next, the polyester film was peeled off to obtain a dried film of the emulsion resin composition. When the oxygen permeability of this film was measured, it was 2.3 cc/m ² ·day·atm.

(Example 9) A film was obtained in the same manner as in Example 8 except that the emulsion resin composition obtained in Example 3 was used. The oxygen transmission rate of this film was 0.15 cc/m ² ·day·atm.

(Comparative Example 4) 300 g of polyoxyethylene nonyl phenyl ether (Emulgen 950 manufactured by Kao Atlas) and 300 g of sodium polyoxyethylene alkylphenyl ether sulfate (Lebenol WZ manufactured by Kao Atlas), 100 g of hydroxyethyl cellulose AL-15 (manufactured by Fuji Chemical), Sodium pyrophosphate 80
g was dissolved in 8,700 g of water, charged into an autoclave of 30 and replaced with ethylene at a pressure of 5 Kg/cm ² . This operation was repeated twice.

Vinyl acetate 8,600g and catalyst ammonium persulfate 2
% Aqueous solution of 2,000 g was added uniformly over 5 hours.

During this period, the ethylene pressure was kept at 40 kg/cm ² and the temperature was kept at 75°C for polymerization, and the mixture was aged for 2 hours at 80°C.

As a result, an ethylene-vinyl acetate copolymer emulsion having a solid content concentration of 51.55% by weight and a viscosity of 3,200 cps was obtained.

The ethylene content was 18 wt% as determined by the alkali saponification method.

Using this emulsion, an ethylene-vinyl acetate resin film was obtained in the same manner as in Example 8. The oxygen transmission rate of this film was measured and found to be 2,000cc/m ² ·da
It was more than y•atm.

(Comparative Example 5) A film was obtained in the same manner as in Example 8 except that the emulsion resin composition obtained in Comparative Example 1 was used. The oxygen transmission rate of this film was 1,850 cc/m ² ·day·atm.

[Effect of the Invention] The resin composition of the present invention is a polyvinyl alcohol-based copolymer resin composition having excellent oxygen barrier properties and capable of being melt-extruded.

In particular, in the production thereof, the polyvinyl alcohol/vinyl acetate/ethylene copolymer, which is the mainstream of the resin which is considered not to be saponified by the conventional vinyl acetate/ethylene copolymer oxygen barrier resin, has a high reaction system during emulsion polymerization. In the present invention, the concentration of the polyvinyl alcohol is relatively low, and the polyvinyl alcohol having a low degree of polymerization is used to avoid the problem of the reaction heat, and the emulsion is used. Is produced, and the emulsion is mixed with an aqueous solution of polyvinyl alcohol to increase the polyvinyl alcohol content in the resin composition, thereby maintaining the oxygen barrier property. It was possible to obtain a resin composition having a barrier property and capable of being melt-extruded.

The resin composition of the present invention is emulsion coatable and melt-extrudable, and therefore, in the field of food packaging materials, pharmaceutical packaging materials, cosmetics, toiletry packaging materials, the resin of the present invention alone or other polyolefin resins and other synthetic resins, It can be widely used by laminating metal foils and the like.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yuichi Yamada, Oita City, Oita Prefecture 2 Nakanosu, Showa Denko Co., Ltd. Oita Laboratory (72) Inventor Akio Harada, 251-1 Ibochu, Ibocho, Tatsuno-shi, Hyogo Wa Polymer Co., Ltd. in Osaka Research Institute (72) Inventor Yoji Tanaka, Ibochu, Ibocho, Tatsuno-shi, Hyogo 251-1 Akira Wa Polymer Co., Ltd. in Osaka Research Institute (72) Takashi Okamoto, Ibocho, Tatsuno-shi, Hyogo Prefecture Middle 251-1 Osaka Research Institute, Showa Polymer Co., Ltd. (56) References JP-A 61-73779 (JP, A) JP-A 60-248764 (JP, A) (58) Fields investigated (Int. . ⁷ , DB name) C08L 31/04 C08L 23/26-23/36 C08L 29/04

Claims (4)

(57) [Claims] 1. A polyvinyl alcohol is used in an amount of 10 relative to the total amount of (A) polyvinyl alcohol and vinyl acetate monomer.
A polyvinyl alcohol emulsion of ethylene-vinyl acetate copolymer having an ethylene content of 1 to 50% by weight with respect to vinyl acetate, obtained by emulsion polymerization of vinyl acetate monomer and ethylene in the presence of 1 to 15% by weight (B). It is characterized in that another polyvinyl alcohol in an aqueous solution is mixed so that the total amount of polyvinyl alcohol units contained in the emulsion resin composition is at least 15% by weight based on the total amount of vinyl alcohol units and vinyl acetate units. Oxygen barrier emulsion resin composition. 2. An emulsion resin composition obtained by mixing (A) the polyvinyl alcohol copolymer emulsion according to claim 1 and (B) polyvinyl alcohol.
Then, an oxygen-barrier resin composition characterized in that a resin solid component is separated. 3. The polyvinyl alcohol (A) has a saponification degree of 70.
The oxygen barrier resin composition according to claim 1 or 2, which has a polymerization degree of 100 to 3,000 and a polymerization degree of 100 to 3,000. 4. The oxygen barrier resin composition according to claim 1 or 2, wherein the polyvinyl alcohol copolymer emulsion has a solid content concentration of 20% by weight or more.