JPH02294309A - Fluorine-containing copolymer and fluorine-based coating consisting essentially thereof - Google Patents

Abstract

PURPOSE:To obtain the subject copolymer, consisting of fluoroolefin units, allyl ester units and hydroxyalkyl vinyl ether units, excellent in solubility in organic solvents and compatibility with curing agents and useful as a coating capable of providing films excellent in gloss and weather resistance. CONSTITUTION:The objective copolymer, obtained by adding a solvent, such as trichlorotrifluoroethane containing a radical polymerization initiator to fluoroolefins (e.g. hexafluoropropene), allyl carboxylates (e.g. allyl acetate) and hydroxyalkyl vinyl ethers (e.g. hydroxybutyl vinyl ether) and carrying out thermal polymerization, containing 20-70mol% fluoroolefin units 5-70mol% units expressed by formula I (R<1> is H or 1-8C hydrocarbon) and 3-40mol% units expressed by formula II (R<2> is 1-6C alkylene; n is 0 or 1) as essential constituent units and having 1000-200000 number-average molecular weight measured by gel permeation chromatography.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a novel fluorine-containing copolymer and a fluorine-based paint containing the same as a main component.

More specifically, the present invention provides a fluorine-containing copolymer that is soluble in an organic solvent, has good compatibility with a curing agent, and is curable at room temperature, and a glossy copolymer containing this copolymer as a main component. It relates to a fluorine-based paint that is hard, has excellent weather resistance, and can form a coating film.

BACKGROUND ART Conventionally, fluorine-containing copolymers have been widely used in many fields because of their extremely excellent heat resistance, mechanical properties, chemical resistance, weather resistance, etc. One of its uses is as a film-forming component in paints. For example, fluororesin paints using tetra-7fluoroethylene polymers, vinylidene heptadide polymers, etc. are known, and these paints have excellent lubricity, non-adhesiveness, weather resistance, and chemical resistance. It is used as a coating material in fields such as the chemical industry, food, architecture, and machinery.

However, the above-mentioned fluororesin paints have the disadvantage of requiring baking at high temperatures, which inevitably limits their range of use. Attempts have been made to develop solvent-based paints using fluorine-containing copolymers with reactive groups.

In order to solubilize a fluoropolymer in an organic solvent, it is necessary to disrupt the crystallinity of the fluoropolymer and internally plasticize it by introducing an appropriate copolymer component. As examples, various copolymers have been disclosed so far (JP-A-61-275311, JP-A-61-57).
No. 609, No. 62-174213, No. 63-
182312). However, in these copolymers, alkyl vinyl ethers and special carboxylic acid vinyl esters are used as copolymerization components, but while these copolymerization components give flexibility to the coating film, they also reduce the hardness of the coating film. In order to achieve this, it is necessary to select a fluoroolefin as a comonomer that does not cause a decrease in hardness, and it also has the drawback of being insufficiently compatible with the curing agent.

Problems to be Solved by the Invention The present invention overcomes the drawbacks of conventional fluorine-containing copolymers soluble in organic solvents, and allows a wide range of fluoroolefins to be selected as monomer components. A new room-temperature-curable fluorine-containing copolymer that also has good solubility in organic solvents and compatibility with curing agents, and a coating film containing this copolymer as a main component that is glossy, hard, and has excellent weather resistance. This was developed with the aim of providing a fluorine-based paint that can provide the following properties.

Means for Solving the Problems The present inventors have conducted intensive research to develop a fluorine-containing copolymer having the above-mentioned preferable properties and a fluorine-based paint containing this copolymer as a main component.
We discovered that this objective could be achieved by using a fluorine-containing copolymer containing a specific vinyl or allyl carboxylic acid ester unit and a specific hydroxyl group-containing unsaturated ether unit, respectively, and based on this knowledge, we developed this book. The invention was completed.

That is, the present invention provides (A) fluoroolefin unit 2
0 to 70 mol%, (B) 5 to 70 mol% of units represented by the general formula (in which R1 is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms), and (C) a unit represented by the general formula (in the formula R″ is an alkylene group having 1 to 6 carbon atoms, and n is 0 or 1
contains 3 to 40 mol% of units represented by
．． 000, and a fluorine-based paint containing this fluorine-containing copolymer as a main component.

The present invention will be explained in detail below.

In the copolymer of the present invention, the fluoroolefin forming the unit (A) is an olefin having at least one fluorine atom in the molecule, and preferably all hydrogen atoms of the olefin are fluorine atoms or other halogen atoms. Examples include perhaloolefins in which atoms are substituted. Further, from the viewpoint of polymerizability and properties of the resulting copolymer, fluoroolefins having 2 or 3 carbon atoms, particularly barfluoroolefins, are suitable.

Specific examples of such fluoroolefins include CH
,-CF! ,CHF1CF! , CHI-CFt, CI!
1 CHF, CCQF - CF. , CHCQ-CF
,,CCQ,-CF. , CCI! F-CCQF,
CHF-CCl2,,CI,DaiCCi2F,C
Fluoroethylene series such as CQ, -CCQF, CF3C
F-CF! , cF3CF-CHF, CF,CH-CF
,, CFsCF-CL, CFsCF-CHF- CHF
zCF-CHF-CFaCH"CI2, CHsCF-C
F2, CHsCH-CFI, CH3CF-CH,, CF
IC12CF=CFx,CF,CC(!-CF,,C
FsCF-CFCi2, CFxCQCCQ-CF,,C
hCQCF-CFCQ, CFC(1*CF-CFx, C
F, CCQ-CCQF, CF3CCO-CC et al., CC
QF,CF−CCQ,,CCQsCF=CFz,CF,
CaCCQ-CCffi,, CFCI! ,CCI-CC
I2j, CF3CF-CHCQ%CC12hCF”CH
C(2, CFsCCQ-CHCQ, CHF*CC12
-CC(lx,CF,OffCH-CCi2,,CF,
CQCCQ-CHCi2. CC(lscF-C
HC(1, CF *QCF − CF *, CFsBr
CH-CFx, CFsCBr-CHBr%CFIC
QCBr-CH*, CI, BrCF-CCl2g, CF
,CBr-CH,,CF*CH=CHBr%CFJrC
7-fluoropropene series such as H=CHF%CFsBrCF-CF, CF, CF, CF-CF, CFsCF''C
FCFs, CFsCH-CFCFs1CFs-CFCF
xCHF*, CF3CFzCF-CHt, CF3CH-
CHCFs, CF! - CFCF*CHs, CF!
- CFCHxCHs, CF3CH! CI-CH*,
CFsCH-CICHI, CFz-CHCHzCH
j, CHsCFxCH-CHt, CFHtCH-CHC
FHg, C}lscFxcH-CHx, CI{. −
CFCI. CI3, CFs (CF*) mCF-CF,,
Fluorooleine compounds having 4 or more carbon atoms such as CFs(CFx)sCF-CF1 can be mentioned, but among these, fluoroethylene compounds and fluoroprobene compounds are preferred, and in particular, tetrafluoroethylene (C
F*-CFx), chlorotrifluoroethylene (C
F, -CFCd) and hexafluoropropene (CF*
-CFCFs) is preferred, and hexa7fluoropropene is preferred from the viewpoint of weather resistance, particularly yellowing resistance upon irradiation with ultraviolet rays, safety, and ease of handling. These fluoroolein may be used alone or in combination of two or more.

In the copolymer of the present invention, the content of units formed from the fluoroolein must be in the range of 20 to 70 mol%, preferably 40 to 60 mol%.

If the content is less than 20 mol%, weather resistance will be insufficient, and if it exceeds 70 mol%, the solubility in organic solvents and the gloss of the cured product will decrease.

In the copolymer of the present invention, the carboxylic acid aryster forming the unit (B) has the general formula CH* = CH
-Cut10 〇-R'...CI)
(R1 in the formula has the same meaning as above) is used. R1 in the general formula (1) has 1 to 1 carbon atoms.
8 aliphatic, alicyclic or aromatic hydrocarbon group.

Specific examples of the carboxylic acid allyl esters include allyl gypsum, allyl acetate, allyl propionate, allyl butyrate, allyl caproate, allyl benzoate, allyl cyclohexanecanoleponate, allyl cyclohexylpropionate, etc. Among these, it is preferable to use those in which the RI is aliphatic or alicyclic because they provide a coating film with high hardness. In this respect, allyl acetate, allyl propionate, and allyl cyclohexylprobionate are particularly suitable. These carboxylic acid allyl esters may be used alone or in combination of two or more.

In the copolymer of the present invention, the content of (B) units is 5 to
It is necessary that the amount is 70 mol%, preferably in the range of 10 to 60 mol%. If the content is less than 5 mol%, the rigidity will be poor and the compatibility with the curing agent will be low, and if it exceeds 70 mol%, the weather resistance will decrease.

In the copolymer of the present invention, the hydroxyl group-containing unsaturated ether forming the unit (C) has the general formula CH, ~CH-(CHs)-OR"-OH
A hydroxyl group-containing vinyl ether or allyl ether represented by (ff)' (R! and n in the formula have the same meanings as above) is used. Specific examples of the hydroxyl group-containing unsaturated ether include hydroxymethyl vinyl ether, hydroxyethyl vinyl ether, 3-hydroxyglopyru vinyl ether, 2-hydroxybutyl vinyl ether, 4-hydroxybutyl vinyl ether, 3-hydroxybutyl vinyl ether, and 2-hydroxybutyl vinyl ether. Examples include hydroxy-2-methylglobin vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, and ethylene glycol monoallyl ether, but among these, those with a vinyl group have a high reactivity with fluoroolefins. It is good and preferred, and 4-hydroxybutyl vinyl ether is particularly preferred. These hydroxyl group-containing unsaturated ethers may be used alone or in combination of two or more.

In the copolymer of the present invention, the content of (C) units is from 3 to
It is necessary that the amount is 40 mol%, preferably in the range of 5 to 35 mol%. If the content is less than 3 mol%, the crosslinking curing time will be long and the chemical resistance, solvent resistance, stain resistance, etc. of the coating film will be insufficient. Not only does the solubility decrease, but when mixed with a curing agent, the gelation time becomes shorter, resulting in a decrease in paint applicability and workability.

The copolymer of the present invention includes the above-mentioned (A), (B) and (C).
In addition to the units, other copolymerizable monomer units may be included if necessary within a range not exceeding 30 mol%. Examples of the copolymerizable monomer include olefins such as ethylene, propylene, and isobutylene, haloolefins such as vinyl chloride and vinylidene chloride, vinyl carboxylate esters such as vinyl acetate and vinyl n-butyrate, and imbropenyl acetate. , carboxylic acid impropenyl esters such as isopropenyl propionate, ethyl vinyl ether, probyl vinyl ether, isopyl vinyl ether, butyl vinyl ether, terL-butyl vinyl ether, pentyl vinyl ether, hexyl vinyl ether, isohexyl vinyl ether, octyl vinyl ether, 4 - Chain-linked alkyl vinyl ethers such as methyl-1-pentyl vinyl ether, cycloalkyl vinyl ethers such as cyclopentyl vinyl ether and cyclohexyl vinyl ether, phenyl vinyl ether, aryl vinyl ethers such as O-, Im-, p-tolyl vinyl ether, penzyl vinyl ether, Aralkyl vinyl ethers such as phenethyl vinyl ether, aromatic vinyl compounds such as styrene and vinyltoluene, silane compounds having a hydrolyzable silyl group and unsaturated bonds such as vinyltrimethoxysilane and alinoretriethoxysilane, hepmaric acid, Di- or monoesters and acid anhydrides of unsaturated bond-containing polybasic acids such as maleic acid, esters of acrylic acid and methacrylic acid such as hydroxyethyl acrylate, hydroxyethyl methacrylate, methyl methacrylate, and glycidyl methacrylate, acrylamide, N - Acrylamides such as methylol acrylamide, allyl glycidyl ether,
Examples include allyl ethers such as ethyl allyl ether, allyl alcohol, and the like. One type of these copolymerizable monomers may be used, or two or more types may be used in combination.

The molecular weight of the fluorine-containing copolymer of the present invention is the number average determined by the Gel Permeability Copolymer 7 (GPC) method using tetrahydrofuran as a solvent and monodispersed polystyrene of known molecular weight as a standard substance. Molecular weight (
crystal) is too~200,000, preferably 2000
~100. It must be in the range of 000.

If the number average molecular weight (Mn) deviates from the above range, the object of the present invention cannot be fully achieved.

The fluorine-containing copolymer of the present invention having such a composition and molecular weight is soluble in organic solvents and has excellent compatibility with a curing agent, and is also effective in cured coatings of paints containing the copolymer as a main component. It is shiny, hard and has excellent weather resistance.

The fluorine copolymer of the present invention can be produced by copolymerizing a monomer mixture of a predetermined ratio in the presence or absence of a solvent using a polymerization initiator, ionizing radiation, etc. as a polymerization initiation source. I can do it.

As the polymerization initiator, water-soluble or oil-soluble ones are appropriately used depending on the type of polymerization and the type of solvent used as desired. As a water-soluble polymerization initiator,
For example, a redox initiator consisting of a persulfate such as potassium persulfate, hydrogen peroxide, or a combination of these with a reducing agent such as sodium bisulfite or sodium thiosulfate, as well as a small amount of iron or ferrous salt. , inorganic initiators such as those coexisting with silver nitrate, dibasic acid peroxides such as diconolambda citric acid peroxide, diglutaric acid peroxide, monosuccinic acid peroxide, and organic initiators such as azobisisobutyramidine dibasic acid salt. Examples include agents. Moreover, as an oil-soluble initiator, for example, t-f. ．． Peroxy ester type peroxides such as tilveroxyisobutyrate and t-butyl peroxyacetate, dialkyl peroxydicarbonates such as diisopropyl peroxydicarbonate, penzoyl peroxide, and azobisisobutyl peroxide. Examples include lonitrile.

The amount of these polymerization initiators to be used is appropriately selected depending on the type thereof, copolymerization reaction conditions, etc., but is 0.005 to 5% by weight, preferably 0.005 to 5% by weight, based on the total amount of monomers normally used.
The amount is selected within the range of 0.05 to 0.5% by weight.

There are no particular restrictions on the polymerization method; for example, bulk polymerization, suspension polymerization, emulsion polymerization, solution polymerization, etc. can be used; From the viewpoint of ease, emulsion polymerization in an aqueous medium, solution polymerization using alcohols such as t-butanol, esters, saturated halogenated hydrocarbons having one or more fluorine atoms, etc. as solvents, A bulk polymerization method that does not require separation from the polymer is preferably used.

When copolymerizing in an aqueous medium, a suspending agent or emulsifier is usually used as a dispersion stabilizer, and a basic buffer is added to adjust the pH value of the reaction solution during polymerization to 4, preferably 6 or higher. It is desirable to do so. Further, addition of a basic substance is also effective in the case of solution polymerization method and bulk polymerization method. Furthermore, there are no particular limitations on the polymerization format, and any of the batch, semi-continuous, and continuous methods can be used.

The reaction temperature in the copolymerization reaction is usually -30 to +15
Within the range of 0'o, it is appropriately selected depending on the polymerization initiation source and the type of polymerization medium. For example, when copolymerization is carried out in an aqueous medium, the temperature is usually in the range of 0 to 100 °C, preferably 10 to 90 °C. selected. In addition, there is no particular restriction on the reaction pressure, but it is usually 1"l00 #g/cra", preferably 2 to 5
0 kg/cm''.Furthermore, the copolymerization reaction can be carried out by adding a suitable chain transfer agent.

The fluorine-containing copolymer of the present invention contains a hydroxyl group as a curing site, and can be used with curing agents used in ordinary thermosetting acrylic paints, such as melamine curing agents, urea resin curing agents, and polybasic acid curing agents. It can be cured by heating using an agent or the like.

Examples of the melamine curing agent include butylated melamine, methylated melamine, epoxy-modified melamine, etc., and those with various degrees of modification are used depending on the purpose, and the degree of self-condensation can also be selected as appropriate. Examples of urea resin curing agents include methylated urea resins and butylated urea resins, and examples of polybasic acid curing agents include long-chain aliphatic radicals. Examples include aromatic polycarboxylic acids, aromatic polycarboxylic acids, and acid anhydrides thereof. Furthermore, blocked polyvalent incyanates can also be suitably used as a curing agent. Further, when using a melamine curing agent or a urea resin curing agent, curing can be accelerated by adding an acidic catalyst.

Furthermore, the fluorine-containing copolymer of the present invention can also be cured at room temperature using polyvalent incyanates. Preferred examples of the polyvalent isocyanates include non-yellowing diisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate, adducts thereof, and polyvalent isocyanates having an isocyanurate ring. Polyhydric incyanates having an isocyanurate ring with good compatibility with the polymer are preferred. When curing at room temperature using these polyvalent incyanates, a known catalyst such as dibutyltin dilaurate can be added to accelerate curing.

The present invention provides a fluorine-based paint containing the fluorine-containing copolymer as a main component, as well as the above-mentioned fluorine-containing copolymer. can be used.

Examples of the solvent include aromatic hydrocarbons such as toluene and xylene, alcohols such as n-butanol, ketones such as methyl isobutyl ketone, glycol ethers such as ethyl cellosolve, and various commercially available thinners. It will be done. Solutions obtained by dissolving the fluorine-containing copolymer in these solvents are colorless and transparent.

This solution type paint is prepared by mixing the fluorine-containing copolymer and a solvent using a mixer commonly used for preparing paints, such as a ball mill, paint shaker, sand mill, jet mill, triple roll, or kneader. This can be done by homogeneously mixing. At this time, if desired,
Pigments, dispersion stabilizers, viscosity modifiers, leveling agents, antigelation agents, ultraviolet absorbers, etc. can also be added.

In addition, when a paint containing the fluorine-containing copolymer as a main component is used as a heat-curable so-called baking paint, melamine, urea resin, polybasic acid or its acid anhydride, block It is used as a one-component paint by adding a hardening agent such as polyvalent incyanate.

On the other hand, in the case of room-temperature curing paints, unblocked polyvalent incyanates are usually used as the curing agent component.
A curing agent liquid containing this curing agent component is separately prepared to form a two-component paint. In this case, l- The paint has a pot life of about 10 hours, cures at room temperature in several hours to several days, and provides a coating film with good physical properties.

Effects of the Invention According to the present invention, a fluoroolefin that has good solubility in organic solvents, good compatibility with a curing agent, and can be cured at room temperature without being subject to any restrictions on the type of fluoroolefin to be used. Fluorine copolymers can be easily provided.

In addition, the fluorine-based paint of the present invention containing the fluorine-containing copolymer as a main component can provide a glossy, hard, and weather-resistant coating film under mild conditions. It is useful as a baking paint for aluminum plates and aluminum sashes, or as an air-drying paint that can be applied on-site.

Furthermore, regarding the material of the base material, including metal materials, inorganic materials such as glass and concrete, FRP, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, nylon, acrylic resin, polyester, ethylene-polyvinyl alcohol copolymer, It is suitably used for coating plastics such as polyvinyl chloride and polyvinylidene chloride, and organic materials such as wood. The fluorine-based paint is also useful in specific applications such as aluminum swimming pools, exterior colored glass, and cement roofs.

Examples Next, the present invention will be explained in more detail with reference to examples.
The present invention is not limited in any way by these examples.

Example 1 After charging 6.9 g of potassium carbonate into a stainless steel autoclave with an internal volume of 112 mm and equipped with a stirrer,
40 g of allyl acetate (hereinafter abbreviated as AAc), 4-1-hydroxybutyl vinyl ether (hereinafter abbreviated as HBVE) 11.
69 and hexa7 fluorine propene (hereinafter abbreviated as RFP)
The internal temperature was raised to 50°C.

Then, diisoprobyl baroxydicarbonate 10
．． 6 g of trichlorotrifluoroethane 39. 7g
After pressurizing the solution dissolved in the autoclave with nitrogen gas, the reaction was continued while stirring, and after 8 hours, the stirring was stopped and the end-reacted heptamer was purged to stop the reaction. Thereafter, the autoclave was opened and the produced copolymer was taken out, washed, and dried. The yield of copolymer was 51N.

The thermal decomposition temperature of the obtained copolymer (temperature at which weight loss begins under heating at 10'0/min in air) was 235°C, and the results of elemental analysis showed that carbon was 44.7% and hydrogen was 4.7%. , fluorine-32
, 7%. Furthermore, in the infrared absorption spectrum of this copolymer, absorptions of 3400c+i-' J: hydroxyl group and carbonyl group at 1760c+m-' were observed, and the hydroxyl group measured according to JIS K-0070 was 38i+9KOH/9. there were. From the above results, it was found that the composition ratio of this copolymer was 34/5B/8 in the molar ratio of HFP units/AAC units/HBVE units. In addition, the number average molecular weight by GPC is 20
It was 00.

10 g of this copolymer was mixed with 11 g of methyl isobutyl ketone.
49 and used as a curing agent “Duranate TPAJ”.
(manufactured by Asahi Kasei Industries, Ltd.) 1.49 was added and mixed. The solution after mixing was clear. This solution was applied to a white tile board using an applicator, dried at room temperature for 30 minutes, and then heated at 100° C. for 6 hours. After heating, a solid and transparent coating film was obtained on the cooled tile board, which was not attacked by wiping with 100 μm of pure methyl isobutyl ketone.

The surface gloss of this coating film according to JIS κ5400 is 60.
The specular reflection was 84%, and the pencil hardness according to JIS K5400 was F.Furthermore, when the hardening property was examined, it was found that the hardening was completed in about 3 days.

Example 2 7.7 g of potassium carbonate was charged into a stainless steel autoclave with an internal volume of 1Q and equipped with a stirrer, and then degassed.
AC86. 29, HBVE259, xylene 235
g, azobisisobutyronitrile (hereinafter abbreviated as AIBN) 0.93g and chlorotrifluoroethylene (hereinafter C
126 g of TFE (abbreviated as TFE) was charged therein, and the internal temperature was raised to 65°C. Thereafter, the reaction was continued while stirring, and after 8 hours, the stirring was stopped and the unreacted monomer was purged to terminate the reaction. Next, the autoclave was opened and the copolymer solution was poured into water to precipitate the copolymer;
Washed and dried. The yield of copolymer was 509.

The composition ratio of this copolymer was determined from the results of elemental analysis, IR analysis, and hydroxyl value measurement, and it was found that CTFE units/AA
c unit/HBVE unit mole is 44/37/19; The molecular weight of this copolymer was 10,000.

When a coating film was formed using this copolymer by the same procedure as in Example 1, the coating film had a surface gloss of 86% and a pencil hardness of H.

Examples 3 to 8 Copolymers were produced in the same manner as in Example 1 using the types and amounts of monomers shown in Table 1.

Yield, molecular weight, composition ratio, and Example 1 of the obtained copolymer
Table 1 shows the transparency, surface gloss, and pencil hardness of the coating films formed in the same manner as above.

Comparative Examples 1 to 5 Using the types and amounts of monomers shown in Table 2, Comparative Examples 1 to 4 were carried out in the same manner as in Example 1, and Comparative Example 5 was further carried out in the same manner as in Example 1.
A copolymer was produced in the same manner as in Example 2 using the type and amount of solvent shown in the table.

The results It is shown in Table 2.

Table 1 Example 9, Comparative Example 6 Using the copolymers obtained in Examples 1 to 4 and Comparative Example 5, coating films were formed in the same manner as in Example 1. Next, this coating film is
A box measuring 40 cm long, 100 cm wide, and 20 Cll high (7) was placed on the floor of an ultraviolet irradiation machine equipped with four GL 15 ultraviolet lamps manufactured by Toshiba Corporation on the top of the box, and the ultraviolet rays were irradiated for 60 hours. Discoloration of the paint film was observed.

The results are shown in Table 3.

Table 3

Claims (1)

[Scope of Claims] 1(A) 20 to 70 mol% of fluoroolefin units, (
B) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (R^1 in the formula is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms) 5 to 70 mol% of units and (C) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, R^2 is an alkylene group with 1 to 6 carbon atoms, n is 0
or 1) as essential constituent units, and the number average molecular weight (@Mn@) measured by gel permeation chromatography is 1000 to 2.
A fluorine-containing copolymer having a molecular weight of 00,000. 2. A fluorine-based paint containing the fluorine-containing copolymer according to claim 1 as a main component.