KR20100005281A - Suspension polymerization method for polyvinylchloride and polyvinylchloride produced thereby - Google Patents

Abstract

PURPOSE: A suspension polymerization method for polyvinylchloride is provided to ensure high polymerization productivity and to prepare a polymer with a small amount of fish eye and excellent initial coloration. CONSTITUTION: A suspension polymerization method for a vinyl chloride polymer comprises the steps of: injecting 50~80% of whole chlorinated vinyl monomer in initial polymerization; and when a polymerization conversion rate is 15~30%, injecting the residual chlorinated vinyl monomer and completing. Based on the chlorinated vinyl monomer 100.0 parts by weight, a solvent, polymerization initiator, and protective colloid preparation are respectively used in the amount of 120-150 parts by weight, 0.02-0.2 parts by weight, and 0.03-5 parts by weight.

Description

Suspension polymerization method for polyvinyl chloride and polyvinylchloride produced thereby

The technical field of the present invention relates to a batch suspension polymerization process for producing a vinyl chloride resin having excellent polymerization productivity and excellent quality such as whiskey and initial coloring property.

Vinyl chloride-based polymers are inexpensive and have excellent quality balance and are used in various fields.

The vinyl chloride polymer is largely divided into a paste resin and a straight resin.

Among them, the paste resin is prepared by an emulsion polymerization method. After homogenizing monomers, water, and surfactants using a homogenizer, the paste resin is transferred to a polymerization apparatus and used for wallpaper, flooring, and the like.

The present invention relates to a straight resin in a vinyl chloride polymer, and unlike the paste resin, is prepared by a suspension polymerization method. Straight resins are used in various fields, such as hard and soft, and in particular, the hard resin is used for pipes, films, window frames, etc., and in soft fields, it is used for wire coating, wrap films, sheets, and the like.

In order to reduce the manufacturing cost of the vinyl chloride polymer, it is important to improve the polymerization productivity per unit volume of the reaction.

As a method of improving the polymerization productivity, the polymerization reaction time is constant and the polymerization conversion rate is increased to increase the output per batch, or the polymerization reaction time is shortened to produce a large amount during the unit time. However, considering that the general conversion rate considering the quality of the vinyl chloride-based polymer is 85 ~ 87%, the method of increasing the polymerization conversion rate is not a great effect in improving the polymerization productivity. Therefore, in order to improve the productivity of the vinyl chloride resin, much efforts have been made to shorten the polymerization reaction time, and at the same time, a stable production method such as polymerization degree, whiskey and initial formation of the vinyl chloride polymer is required. have. However, the conventionally known method for producing a vinyl chloride-based polymer has a problem in that the polymerization productivity is excellent but insufficient in securing stable quality.

In order to increase the polymerization conversion rate of the vinyl chloride-based polymer, a method of adding an initiator at the time of lowering the internal pressure has been proposed. However, the time when the pressure inside the polymerization reactor is lowered is 70% or more, so There was a problem that the added initiator does not sufficiently react with the vinyl chloride monomer, so that the amount of whiskey increases or the fine particles increase, thereby lowering the initial colorability.

In addition, a method of introducing an initiator having a short half-life into the middle of the reaction as a method of shortening the polymerization reaction time of the vinyl chloride polymer has been proposed, but considering that the vinyl chloride monomer is prepared by radical polymerization, Because of the rapid growth and the growth gradually weakens toward the second half of the polymerization, this method also causes a problem that the initial colorability decreases due to the increase in the amount of fine grains or the increase of fine particles.

The problem to be solved by the present invention is a method for preparing a vinyl chloride-based polymer by suspension polymerization of a vinyl chloride-based monomer, vinyl chloride comprising the step of continuously adding a vinyl chloride monomer by controlling the proportion of the initially added vinyl chloride monomer It is to provide a method for producing a polymer.

In the suspension polymerization method of the vinyl chloride monomer according to the present invention, 50 to 80% of the total amount of the vinyl chloride monomer is added to the initial stage of the polymerization of the vinyl chloride monomer, and when the polymerization conversion rate is 15 to 30%, the remaining vinyl chloride monomer is started to be added. And completing.

In addition, with respect to 100 parts by weight of the vinyl chloride monomer, 120 to 150 parts by weight of the solvent, 0.02 to 0.2 parts by weight of the polymerization initiator, the protective colloid preparation may be reacted using 0.03 to 5 parts by weight.

In addition, the protective colloid preparation is a vinyl alcohol resin having a hydration degree of 30 to 90% by weight and a viscosity of 4% aqueous solution at 10 to 60 cps at room temperature, and a 3% to 20% by weight propyl hydroxide and 2% aqueous solution measured at room temperature. May be selected from polymers of cellulose and unsaturated organic acids having a viscosity of 10 to 20,000 cps.

In addition, the polymerization initiator is diacyl peroxide, including dicumyl peroxite, di-3,5,5-trimethyl hexanoyl peroxide, dilauroyl peroxide, diisopropyl peroxydicarbonate, di-sec- Peroxydicarbonates containing butyl peroxydicarbonate and di-2-ethylhexyl peroxydicarbonate, peroxy esters containing t-butylperoxy pivalate and t-butylperoxy neodecanoate, and azo It can be selected from azo compounds including bis-2,4-dimethylvaleronitrile and sulfates including potassium persulfate and ammonium persulfate.

In addition, it may further include a vinyl monomer copolymerizable with the vinyl chloride monomer.

The vinyl monomer copolymerizable with the vinyl chloride monomer may be used alone or in an olefin compound including ethylene, propylene, vinyl acetate, vinyl esters, acyclic nitriles, vinyl alkyl ethers, unsaturated fatty acids, and anhydrides of fatty acids. It may be used by mixing more than one species.

In addition, the polymerization regulator, chain transfer agent, PH regulator, antioxidant, crosslinking agent, antistatic agent, scale control agent, may further include a surfactant.

In addition, the temperature at the time of polymerization may be 30-80 degreeC.

In addition, the vinyl chloride polymer according to the present invention is produced by the above production method.

According to the present invention, while the productivity is improved, there is little production of whiskey, and the initial coloring property is excellent.

The present invention provides a method for producing a vinyl chloride polymer having higher productivity. In particular, the vinyl chloride-based polymer produced by the production method according to the present invention, in addition to the improvement in productivity, has little occurrence of whiskey, and is excellent in initial coloring property and the like.

The vinyl chloride polymer according to the present invention is prepared by a suspension polymerization method, and may be made of purely vinyl chloride monomer, but may be composed of a vinyl chloride monomer as a mixture with a vinyl monomer copolymerizable therewith. Can be. When prepared as a mixture of a vinyl chloride monomer and a copolymerizable vinyl monomer, the content of the vinyl chloride monomer may be 50% by weight or more.

Vinyl monomers copolymerizable with the vinyl chloride monomer include olefin compounds such as ethylene and propylene, vinyl esters such as vinyl acetate and vinyl propionate, unsaturated nitriles such as acrylonitrile, vinyl methyl ether and vinyl ethyl ether. In general, unsaturated monomers such as alkyl ethers, acrylic acid, methacrylic acid, itaconic acid, maleic acid, and anhydrides of these fatty acids, and monomers copolymerizable with vinyl chloride monomers can be used alone or in combination of two or more thereof.

In the suspension polymerization method of the vinyl chloride polymer according to the present invention, the initial ratio of the vinyl chloride monomer is adjusted to 50 to 80% of the total amount of the vinyl chloride monomer, and the vinyl chloride monomer remaining in the polymerization conversion rate of 15 to 30% is continuously Adding.

Specifically, the input ratio of the initial vinyl chloride monomer is preferably 50 to 80% of the total amount of the vinyl chloride monomer input, but particularly preferably 60 to 70% of the total amount of the vinyl chloride monomer input. In addition, it is preferable to continuously add the vinyl chloride monomer in a polymerization conversion period of 15 to 30%, and it is particularly preferable that both the starting point and the completion point of the vinyl chloride monomer are 15 to 30%.

If the initial ratio of the vinyl chloride monomer is less than 50% of the total amount of the vinyl chloride monomer, the fine particles are increased and the initial colorability is deteriorated, and the polymerization time by the continuously added vinyl chloride monomer is too long to increase the polymerization productivity per batch. Insignificant When the input ratio of the initial vinyl chloride monomer is more than 80% of the total amount of the vinyl chloride monomer input, since the addition of the vinyl chloride monomer continuously added later, the effect of increasing the polymerization productivity per batch is insignificant.

In addition, when a continuous addition of vinyl chloride monomer is added at a time when the polymerization conversion rate is less than 15%, the decrease in volume shrinkage of the polymerization reaction system is too small due to the polymerization reaction, so that the amount of vinyl chloride monomer that can be added continuously is limited to a small amount per batch. The effect of increasing the polymerization productivity is insignificant.

When the vinyl chloride monomer is converted into a vinyl chloride polymer by the polymerization reaction, the specific gravity of the vinyl chloride polymer is large, so that the polymerization reaction proceeds and the volumetric shrinkage of the polymerization reaction system occurs. The volumetric shrinkage of the polymerization reaction system is as follows. It can be calculated from

V = M * C / 100 * (1 / d ₁ -1 / d ₂ )

In the above formula, V is the volume shrinkage due to the polymerization reaction, M is the vinyl chloride monomer weight, C is the polymerization conversion rate of the vinyl chloride monomer to the vinyl chloride polymer, d ₁ is the specific gravity of the vinyl chloride monomer, d ₂ is the vinyl chloride polymer Indicates the specific gravity.

Continuous addition of a vinyl chloride monomer in a period in which the polymerization conversion rate exceeds 30% makes it difficult to control the physical properties of the final vinyl chloride polymer, and thus it is difficult to manufacture high quality vinyl chloride polymer having stable quality such as whiskey and initial coloring properties.

That is, since polymerization and re-dispersion occur most actively at a polymerization conversion of less than 30%, it is possible to control the internal shape of the polymer particles. Thus, by adding an additional vinyl chloride monomer during this period, the added vinyl chloride monomer is stable in the form of vinyl chloride. It can be expected to increase the polymerization productivity per batch by converting to a polymer.

The vinyl chloride polymer is prepared by including a vinyl chloride monomer, a protective colloid preparation, a polymerization initiator, and a hydrogen ion concentration regulator.

The protective colloid preparation is used to stably maintain the vinyl chloride polymer manufacturing process and to obtain stable particles, and has a hydration degree of 30 to 90% by weight and a vinyl alcohol having a viscosity of 10% to 60 cps in a 4% aqueous solution at room temperature. Systemic resins and propyl hydroxides may be 3 to 20% by weight, cellulose having a viscosity of 10 to 2,000 cps in a 2% aqueous solution measured at room temperature, a polymer of unsaturated organic acid, or the like. Specific examples thereof may be one selected from acrylic acid polymers, methacrylic acid polymers, itaconic acid polymers, fumaric acid polymers, maleic acid polymers, succinic acid polymers, gelatin, or a mixture of two or more thereof.

The protective colloid preparation is preferably included in an amount of 0.03 to 5 parts by weight, and more preferably 0.05 to 2.5 parts by weight, based on 100 parts by weight of the total vinyl chloride monomer. When used in the above content does not form a huge particle does not generate a whiskey, there is no increase of fine particles has an excellent initial coloring properties.

Initiators usable in the present invention include diacyl peroxides such as dicumyl peroxide, dipentyl peroxide, di-3,5,5-trimethyl nucleoanoyl peroxide, dilauroyl peroxide, and diisopropyl peroxydicarbonate. , Peroxy dicarbonates such as di-sec-butyl peroxy dicarbonate, di-2-ethylhexyl peroxy dicarbonate, or peroxy esters such as t-butyl peroxy pivalate and t-butyl peroxy neodecanoate And azo compounds such as azobis-2,4-dimethylvaleronitrile, sulfates such as potassium persulfate and ammonium persulfate, and the like, and can be used alone or in combination of two or more thereof. The amount of use is determined by factors such as manufacturing process, productivity, and quality. Generally, the total amount of initiator can be used in an amount of 0.02 to 0.2 parts by weight, most suitably 0.04 to 0.12 based on 100 parts by weight of the total amount of vinyl chloride monomer added. The use of parts by weight is preferred.

When the amount of the initiator is less than 0.02 parts by weight, the reaction time is delayed and productivity is lowered. When the amount of the initiator is used more than 0.2 parts by weight, the initiator is not completely consumed during the polymerization process and remains in the final resin product to improve the thermal stability and color quality of the resin. Lowers.

Antioxidants usable in the present invention are not particularly limited as long as they are generally used in the preparation of the vinyl chloride-based polymer, and non-limiting examples thereof are triethylene glycol-bis- [3- (3-t-butyl-5). -Methyl-4-hydroxy phenyl) propionate], hydroquinone, p-methoxy phenol, t-butylhydroxyanisole, n-octadecyl-3- (4-hydroxy 3,5-di-t -Butyl phenyl) propionate, 2,5-di-t-butyl hydroquinone, 4,4-butylidenebis (3-methyl-6-t-butyl phenol), t-butyl catechol, 4,4 Phenolic compounds such as -thio bis (6-t-butyl-m-cresol), tocopherol, and nojihydroguairecin acid, N, N-diphenyl-p-phenylene diamine, 4,4-bis (dimethyl benzyl Amine compounds such as diphenyl amine, sulfur compounds such as dodecyl mercaptan, 1,3-diphenyl-2-thiol and the like can be used alone or in combination of two or more thereof.

In the present invention, a polymerization regulator, a chain transfer agent, a pH regulator, an antioxidant, a crosslinking agent, an antistatic agent, a scale control agent, a surfactant, and the like may be added to the polymerization system before or after the polymerization, if necessary. You may add a part partly or continuously to a polymerization system.

In general, the polymerization degree of the vinyl chloride-based polymer is determined by the polymerization reaction temperature, and the polymerization degree is a factor that greatly affects the processing conditions and the physical properties of the product, so an appropriate polymerization temperature should be selected. The general polymerization temperature range of the vinyl chloride polymer produced for commercial purposes is preferably 30 to 80 ° C.

As the reactor used in the present invention, the shape of the stirring device such as a stirrer and a baffle is not particularly limited, and a stirring device generally used for suspension polymerization of a vinyl chloride polymer can be used. Specific examples of the stirrer include stirring paddles, paddle paddles, pitched paddle pads, bloomers gin pads, pudora rams, turbine pads, propeller pads, or the like. Stirrers combined with more than one stirring blade may be used, and baffles may be plate-shaped, cylindrical, D-shaped, looped, or finger-type.

The prepared vinyl chloride polymer slurry may be prepared as a final vinyl chloride polymer by removing moisture with a fluidized bed dryer under conventional reaction conditions.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments to assist in understanding the present invention. However, the following examples are only for illustrating the present invention and the present invention is not limited thereto.

(Examples 1 to 6)

Example  One

Of deionized water in internal volume of 1m ³ reactor having a reflux condenser 390kg, 2- ethylhexyl peroxydicarbonate 130g, dilauryl peroxide 20g, moisture content of 80% and a polyvinyl alcohol, the viscosity of 4% aqueous solution at room temperature 30cps 200g was added to the reactor at once, vacuum was applied, 230 kg of vinyl chloride monomer was added thereto, and the reaction temperature was increased to 57 ° C., and the reaction proceeded while maintaining the whole polymerization reaction. 120 kg was added continuously. After the polymerization reactor pressure reached 6.0 kg / cm ² , 60 g of antioxidant was added, and then unreacted monomer was recovered and the polymer slurry was recovered in the polymerization reactor. The slurry thus obtained was dried in a fluidized bed dryer in a conventional manner to obtain a vinyl chloride polymer.

Example  2

240 kg of vinyl chloride monomers were initially charged, and polymerization was carried out under the same conditions as in Example 1 except that 120 kg of vinyl chloride monomers were continuously added in a polymerization conversion period of 15 to 30%.

Example  3

230 kg of vinyl chloride monomers were initially charged, and polymerization was carried out under the same conditions as in Example 1 except that 150 kg of vinyl chloride monomers were continuously added in a polymerization conversion period of 15 to 30%.

Example  4

The polymerization was carried out under the same conditions as in Example 1 except that 250 kg of vinyl chloride monomer was initially added, and 130 kg of vinyl chloride monomer was continuously added in the polymerization conversion period of 15 to 30%.

Example  5

280 kg of vinyl chloride monomer was initially charged, and polymerization was carried out under the same conditions as in Example 1 except that 120 kg of vinyl chloride monomer was continuously added in a polymerization conversion period of 15 to 30%.

Example  6

The polymerization was carried out under the same conditions as in Example 1 except that 260 kg of vinyl chloride monomer was initially added and 140 kg of vinyl chloride monomer was continuously added in the polymerization conversion period of 15 to 30%.

In the above examples, the initial vinyl chloride monomer input ratio was about 65.7% of Example 1, about 66.6% of Example 2, about 60.5% of Example 3, about 65.7% of Example 4, about 70% of Example 5, Example 6 was 65%, and Comparative Example 1 was initially injected in its entirety, Comparative Example 2 was about 48.5%, Comparative Example 3 was 90.9%, Comparative Example about 94%, and Comparative Example 5 was about 65.7%.

(Comparative Example 1 to Comparative Example 6)

Comparative example  One

200 g of polyvinyl alcohol with a reflux condenser in a 1 m3 reactor, 390 kg of deionized water, 130 g of 2-ethylhexyl peroxydicarbonate, 20 g of dilauryl peroxide, 80% of hydration and 30 cps of a viscosity of 4% aqueous solution at room temperature Was added to the reactor, vacuum was added, and then 300 kg of vinyl chloride monomer was added thereto, and the reaction temperature was increased to 57 ° C. to maintain the whole polymerization reaction. The reaction was carried out at the time when the polymerization reactor pressure reached 6.0 kg / cm ² . After adding 60 g of antioxidant, unreacted monomer was recovered and the polymer slurry was recovered in the polymerization reactor. The slurry thus obtained was dried in a fluidized bed dryer in a conventional manner to obtain a vinyl chloride polymer.

Comparative example  2

The polymerization was carried out under the same conditions as in Example 1 except that 170 kg of vinyl chloride monomer was initially added and 180 kg of vinyl chloride monomer was continuously added in the polymerization conversion period of 15 to 30%.

Comparative example  3

The polymerization was carried out under the same conditions as in Example 1 except that 300 kg of vinyl chloride monomer was initially added, and 30 kg of vinyl chloride monomer was continuously added in the polymerization conversion period of 15 to 30%.

Comparative example  4

The polymerization was carried out under the same conditions as in Example 1 except that 300 kg of vinyl chloride monomer was initially added, and 20 kg of vinyl chloride monomer was continuously added in the polymerization conversion period of 5 to 15%.

Comparative example  5

230 kg of vinyl chloride monomers were initially charged, and polymerization was carried out under the same conditions as in Example 1 except that 120 kg of vinyl chloride monomers were continuously added in a polymerization conversion period of 40 to 50%.

Comparative example  6

Initially, 300 kg of vinyl chloride monomer was added, 50 kg of vinyl chloride monomer was added at a polymerization conversion rate of 15 to 30%, and 50 kg of vinyl chloride monomer was added at a polymerization conversion rate of 30 to 80%, the same as in Example 1. Polymerized under conditions.

Experimental Example

Measurement results of specific experimental conditions, basic physical properties, and processed physical properties of the results according to the examples and the comparative examples are shown in Tables 1 and 2 below.

In this experiment, the physical properties were evaluated by the following method.

Polymerization Productivity Evaluation : The amount of PVC polymer produced per unit time of production per batch was measured.

Polymerization Measurement : Measured according to ASTM D1243-79.

Average particle size measurement : measured by ASTM D1705.

Early Coloring  evaluation

To 100 parts by weight of the polymer, 1 part by weight of a tin stabilizer, 0.5 part by weight of a lead stabilizer, 1.5 parts by weight of a stabilizer, and 45 parts by weight of a plasticizer were mixed and kneaded at 150 ° C. for 5 minutes using a roll, followed by sheeting. Got. This sheet was cut, stacked, and pressed to form a compressed sheet. This was visually observed and evaluated according to the following criteria.

(Double-circle): The level of coloring similar to this and the level which is satisfactory practically based on the comparative example 1.

(Circle): Based on the comparative example 1, although it is slightly inferior, it is the coloring degree of the abnormality level, and there is no problem in practical use.

X: The level of coloring is different compared with Comparative Example 1, and the level of practical problems in which the color tone is different.

Fish-eye sheep

After mixing and kneading 100 parts by weight of vinyl chloride polymer, 45 parts by weight of DOP (Dioctyl Phthalate), 0.1 part by weight of barium stearate, 0.2 part by weight of tin stabilizer, and 0.1 part by weight of carbon black using a 6-inch roll at 140 ° C. for 6 minutes, A sheet having a thickness of 0.3 mm was made and represented by the number of white transparent particles in 100 cm ² of this sheet.

Examples 1 to 6 showed almost the same level of results in terms of polymerization degree, average particle size, whiskey and initial colorability, and the polymerization yield per unit time was also high overall.

As described above, it can be seen that the polymerization production amount was significantly increased as compared with the comparative examples. In the case of Comparative Example 1 is a conventional polymerization method in which all the initial amount of the vinyl chloride monomer is added, in the case of Comparative Example 2, the polymerization time by the addition of the vinyl chloride monomer added continuously because the addition rate of the initial vinyl chloride monomer is too long per batch It was found that the polymerization productivity hardly increased. In addition, the initial colorability deteriorated. In the case of Comparative Example 3, the addition ratio of the initial vinyl chloride monomer is too large, so that the additional amount of the vinyl chloride monomer added continuously is reduced, so that the effect of increasing the polymerization productivity per batch is insignificant. In the case of Comparative Example 4, since the addition of the vinyl chloride monomer in the polymerization conversion rate of less than 15% when the addition of the continuous chloride to the vinyl chloride monomer can be reduced, the effect of increasing the polymerization productivity per batch is insignificant. In the case of Comparative Example 5, the vinyl chloride monomer was further added during the polymerization conversion period of 30% or more to increase the amount of whiskey, and the effect of increasing productivity was minimal. In the case of Comparative Example 6, the timing of the addition of the vinyl chloride monomer was 15 to 30%, but the polymerization time was too long as the completion of the addition when the polymerization conversion was 80%, and the number of volatilises increased. Could.

Claims (9)

50-80% of the total amount of the vinyl chloride monomer is added to the initial stage of the polymerization of the vinyl chloride monomer, and when the polymerization conversion rate is 15-30%, the vinyl chloride polymer suspension polymerization method including starting and completing the addition of the remaining vinyl chloride monomer. . The method according to claim 1, With respect to 100 parts by weight of the vinyl chloride monomer, 120 to 150 parts by weight of the solvent, 0.02 to 0.2 parts by weight of the polymerization initiator, 0.03 to 5 parts by weight of the protective colloid preparation is reacted with vinyl chloride polymer suspension polymerization Way. The method according to claim 2, The protective colloid preparation is a vinyl alcohol resin having a degree of hydration of 30 to 90% by weight and a viscosity of 4% aqueous solution at 10 to 60 cps at room temperature, and a 3% to 20% by weight of propyl hydroxide and a viscosity of 2% aqueous solution measured at room temperature. The vinyl chloride polymer suspension polymerization method characterized in that it is selected from the polymer of cellulose and unsaturated organic acid of 10 to 20,000 cps. The method according to claim 2, The polymerization initiator is diacyl peroxide including dicumyl peroxite, di-3,5,5-trimethyl hexanoyl peroxide, dilauroyl peroxide; Peroxydicarbonates containing diisopropyl peroxydicarbonate, di-sec-butylperoxydicarbonate, di-2-ethylhexyl peroxydicarbonate; peroxy esters including t-butylperoxy pivalate and t-butylperoxy neodecanoate; An azo compound including azobis-2,4-dimethylvaleronitrile; And A vinyl chloride polymer suspension polymerization method characterized in that it is selected from sulfates including potassium persulfate and ammonium persulfate. The method according to claim 1, A vinyl chloride polymer suspension polymerization method further comprising a vinyl monomer copolymerizable with a vinyl chloride monomer. The method according to claim 5, The vinyl monomer copolymerizable with the vinyl chloride monomer may be used alone or in combination of an olefin compound containing ethylene and propylene, vinyl acetate, vinyl esters, acyclic nitriles, vinyl alkyl ethers, unsaturated fatty acids, and anhydrides of fatty acids. Vinyl chloride polymer suspension polymerization method characterized in that it is used by mixing. The method according to claim 2, A vinyl chloride polymer suspension polymerization method further comprising a polymerization regulator, a chain transfer agent, a pH regulator, an antioxidant, a crosslinking agent, an antistatic agent, a scale control agent, and a surfactant. The method for producing a vinyl chloride polymer according to claim 1, wherein the polymerization temperature is 30 to 80 ° C. The vinyl chloride polymer manufactured by the manufacturing method according to any one of claims 1 to 8.