JPH0241550B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to compositions of hydrolyzable silyl-terminated polyethers that can cure into rubber-like materials on contact with moisture. The present inventors have already discovered that a silyl group-terminated polyether consisting of one atom of Si at the end and having a hydrolyzable group on the Si atom can be a room-temperature curable composition useful as a sealant, etc. reported (Japanese Unexamined Patent Publication No. 1973
-73998, Japanese Patent Application Publication No. 1973-129247, Japanese Patent Publication No. 1973-6097,
(Japanese Patent Publication No. 56-21458). By adding a diorganopolysiloxane having a hydroxyl group or a hydrolyzable group bonded to a Si atom to the polyether at the end of such a silyl group, it is possible to easily adjust the tensile properties such as strength and elongation of the cured product of the polyether. Effects such as improvement of residual tack (reducing stickiness on the surface of the cured product and preventing adhesion of dust, etc.) can be obtained. The present invention uses a silyl group-terminated polyether which has two or more Si atoms at the end and has a hydrolyzable group on the Si atom, and uses a hydroxyl group bonded to the Si atom. It has been discovered that the addition of a diorganopolysiloxane having a hydrolyzable group or a diorganopolysiloxane further improves the residual tack of the cured product, and also improves the resilience of the cured product against deformation. That is, the present invention provides (a) the following formula (Here, R〓 is a divalent organic group having 1 to 20 carbon atoms; R〓 is hydrogen or a monovalent organic group having 1 to 20 carbon atoms; R〓 is the same or different monovalent hydrocarbon group or Triorganosiloxy group; a is 0, 1,
2 or 3, b is 0, 1 or 2, c is 0 or 1, provided that 1a+b4; X is a different or similar hydrolyzable group; m is an integer selected from 0 to 18 have at one end,
The main chain is essentially composed of chemically bonded repeating units represented by the following formula -R〓-O- (2) (where R〓 is a divalent hydrocarbon group having 1 to 4 carbon atoms) For 100 parts by weight of polyether with a molecular weight of 500 to 15,000, 200 parts by weight or less of formula (B) (Here, R is the same or different monovalent hydrocarbon group; n is a positive integer of 19 or more; d is 0, 1, or 2; Y is a hydroxyl group or the same or different hydrolyzable group) The present invention provides a room temperature curable composition containing a diorganopolysiloxane represented by: The present invention will be explained in detail below. In the present invention, the silyl group-terminated polyether represented by formula (1) is A silicon hydride compound represented by the formula Addition reaction of a polyether having a terminal olefin group represented by the formula with a platinum-based compound such as platinum black, chloroplatinic acid, platinum alcohol compound, platinum olefin complex, platinum aldehyde complex, platinum ketone complex, etc. as a catalyst. Basically, it can be manufactured by In formula (4), R〓 is the same or different monovalent hydrocarbon group having 1 to 20 carbon atoms, such as an alkyl group such as methyl or ethyl, a cycloalkyl group such as cyclohexyl, an aryl group such as phenyl group, or a benzyl group. It is selected from aralkyl groups such as, and also includes a triorganosiloxy group represented by the formula (R') ₃ SiO-. In the formula, R' represents the same or different monovalent hydrocarbon groups having 1 to 20 carbon atoms. In formula (4), X represents a different or the same type of hydrolyzable group, including a halogen group, hydride group, alkoxy group, acyloxy group, ketoximate group, amide group, acid amide group, aminooxy group, and mercapto group. , alkenyloxy group, etc. Specifically, the silicon hydride compound represented by formula (4) includes trimethylsiloxydichlorosilane,
1,3,3,5,5,7,7-heptamethyl-
Examples include 1,1-dimethoxytetrasiloxane, trimethylsiloxymethylacetoxysilane, bis(diethylketoximate)trimethylsiloxysilane, and bis(dicyclohexylketoximate)trimethylsiloxysilane. In the present invention, a silicon hydride compound of formula (4) and a silicon hydride compound of formula (4)
After reacting with the polyether having a terminal olefin group (5), it is also possible to use a product in which some or all of the X groups are further converted to other hydrolyzable groups. For example, when the X group is a halogen group or a hydride group, it is preferable to convert it into an alkoxy group, acyloxy group, aminooxy group, alkenyloxy group, etc. before use. In formula (5), R〓 is a hydrogen atom or a carbon number of 1 to
20 monovalent organic groups, preferably a hydrogen atom or a hydrocarbon group. Furthermore, a hydrogen atom is particularly preferred.
In formula (5), R〓 is the same or different divalent organic group having 1 to 20 carbon atoms, and includes hydrocarbon groups, ether bonds, ester bonds, urethane bonds,
Hydrocarbon groups containing carbonate bonds are preferred.
A methylene group is particularly preferred. A specific method for producing the terminal-containing polyether represented by formula (5) is disclosed in JP-A-Sho.
54-6097 by the present inventors. R〓 shown in formula (2) is a divalent hydrocarbon group having 1 to 4 carbon atoms, but specifically -CH ₂
−, −CH ₂ CH ₂ −,

【formula】

【formula】

[Formula] - CH ₂ CH ₂ CH ₂ CH ₂ - and the like. The polyether may consist of only one type of repeating unit, or a polyether consisting of two or more types of repeating units is effectively used. especially

[Formula] is preferred. Polyether having a molecular weight of 500 to 15,000 can be effectively used, but preferably 3,000 to 12,000.
It is preferable to have a molecular weight of . Such polyether can be produced by the method disclosed in JP-A-53-129247 and JP-A-54-6097. In the present invention, the diorganopolysiloxane represented by the formula (3), which is the component (b), is used to control tensile properties such as strength and elongation of the cured silyl-terminated polyether, to improve ultraviolet resistance, and to improve UV resistance. It can be effectively used for improving resilience against deformation and deformation. In particular, the restorability against residual tack and deformation is superior to that in the case of using a silyl-terminated polyether whose terminal end consists of one atom of Si. This is presumed to be because component (a) has a large number of silicon atoms, which increases its compatibility with component (b). In formula (3), R〓 is the same or different monovalent hydrocarbon group, such as an alkyl group such as methyl or ethyl, a cycloalkyl group such as cyclohexyl, an aryl group such as phenyl group, or an aralkyl group such as benzyl group. To be elected. The number of carbon atoms is preferably 1 to 20. Particularly preferred are methyl group and phenyl group.
A functional group Y exists at the end of the diorganopolysiloxane represented by formula (3). The Y group is a hydroxyl group or a hydrolyzable group of the same or different type, but silanol-terminated diorganopolysiloxanes in which d=2 and Y is a hydroxyl group are particularly preferred. The diorganopolysiloxane represented by formula (3) is preferably liquid, and any diorganopolysiloxane having a centistoke of 500,000 centistrokes or less at 25°C can be used. The amount used is
It can be used in an amount of up to 200 parts by weight per 100 parts by weight of the silyl-terminated polyether, but from the viewpoint of changing the properties of the silyl-terminated polyether, it is preferably used in an amount of up to 50 parts by weight.
They may be used alone or in combination of two or more. In the present invention, the diorganopolysiloxane shown in (B) is usually added and used at the time of compounding, but it is added in advance to the silyl-terminated polyether in (B) and subjected to pretreatment such as heating. It also includes using it after it has grown old. In particular, when the functional group Y in the diorganopolysiloxane compound represented by (b) is a hydroxyl group, it is easier to achieve the desired effect by mixing the silyl-terminated polyether in advance and subjecting it to heat treatment. In the present invention, in order to achieve the adjustment of tensile properties such as strength and elongation of the cured silyl-terminated polyether and the improvement of adhesive properties, Y groups bonded to silicon atoms (Y groups are hydroxyl groups or A silicon compound having at least one hydrolyzable group in one molecule and having 1 to 20 silicon atoms (hereinafter also referred to as component (iii)) may be used in combination. The silicon compound has one Y group bonded to a silicon atom.
It is a compound consisting of 1 to 20 silicon atoms having at least one silicon atom in the molecule, and has the formula SiR〓 _p Y _4-p (6) (where R〓 is a divalent organic group having 1 to 12 carbon atoms;
Y is a hydroxyl group or a hydrolyzable group of the same or different type; p is an integer of 0, 1, 2 or 3)
Examples include a compound having one silicon atom represented by the formula, or a branched, network, cyclic, or linear organopolysiloxane compound having 2 to 20 silicon atoms. R〓 in formula (6) is an organic group bonded to a silicon atom through a silicon-carbon bond, and the organic group includes a halogen group, hydroxyl group, alkoxy group, nitrile group, amino group, mercapto group, etc. It may contain functional groups such as a group, an acid amide group, a carboxylic acid group, an epoxy group, an acryloyl group, and the like. Y is a group selected from a halogen group, a hydride group, a hydroxyl group, an alkoxy group, an acyloxy group, a ketoximate group, an amide group, an acid amide group, an aminooxy group, an alkenyloxy group, and a mercapto group, but especially a hydroxyl group, an alkoxy Groups are preferred. To give a concrete example, CH ₂ =CHSi
(OCH ₃ ) ₃ , CH ₂ = CHSi (OCH ₂ CH ₂ OCH ₃ ) ₃ , CH ₂ = CHSiCH ₃ (OCH ₂ CH ₃ ) ₂ , H ₂ NC ₂ H ₄ NHC ₃ H ₆ SiCH ₃ (OCH ₃ ) ₂ , ClC ₂ H ₄ Si
( _OCH3 ) ₃ , _HSC3H6Si ( _OEt ) ₃ ,Si
(OCH ₂ CH ₂ CH ₂ CH ₃ ) ₄ ,

Examples include [Formula], but are not limited to these. Also, 2 in one molecule
It may contain more than one type of R and Y groups. Furthermore, an organopolysiloxane having 2 to 20 silicon atoms may also be used, but the organo group may have 1 to 20 carbon atoms selected from alkyl groups, aryl groups, etc.
Particularly preferred are 12 monovalent hydrovalent groups. It is sufficient that the organopolysiloxane contains at least one Y group, but it is particularly preferable that it contains one to six Y groups. As the Y group, a hydride group, a hydroxyl group, and an alkoxy group are particularly preferred. One type of organo group and Y group may be contained in one organopolysiloxane molecule, or two or more types thereof may be contained. Specific examples of organopolysiloxane compounds include

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

The compounds include, but are not limited to, these compounds. Component (c) is the silyl-terminated polyether of component (a)
It is used in an amount of 0 to 20 parts by weight per 100 parts by weight, and preferably 0 to 10 parts by weight. The silicon compound may be used alone or in combination of two or more types. A cured product of a composition containing a large amount of Y groups in one molecule increases modulus and adhesiveness, and
A cured product of a composition containing fewer groups has the effect of lowering the modulus. The method of adding component (c) is the same as the method of adding component (b) above, and the effects are also the same. In curing the composition of the present invention, a silanol condensation catalyst may or may not be used.
If condensation catalysts are used, alkyl titanates; organosilicon titanates; metal salts of carboxylic acids such as tin octylate, dibutyltin laurate and dibutyltin maleate, dibutyltin phthalate; dibutylamine-2-ethyl Known silanol condensation catalysts such as amine salts such as xoates; and other acidic and basic catalysts are usefully used. The amount of these condensation catalysts used is preferably 0 to 10 parts by weight per 100 parts by weight of the silicon-terminated polyether. When an alkoxy group is used as the hydrolyzable group, the curing rate is slow if this polymer alone is used, so it is preferable to use a condensation catalyst. In this case, a tin carboxylate is particularly preferred as the condensation catalyst. The composition of the present invention can be modified by incorporating various fillers. Fillers include reinforcing fillers such as fume silica, precipitated silica, anhydrous silicic acid, hydrous silicic acid and carbon black; calcium carbonate, magnesium carbonate, diatomaceous earth,
Fillers such as calcined clay, clay, talc, titanium oxide, bentonite, organic bentonite, ferric oxide, zinc oxide, activated zinc white, hydrogenated castor oil and shirasu balloons; fibrous materials such as asbestos, glass fibers and filaments. Fillers can be used. If you want to obtain a hardened composition with high strength using these fillers, use mainly fume silica, precipitated silica, anhydrous silicic acid, hydrated silicic acid, carbon black, surface-treated fine calcium carbonate, calcined clay,
Add 1 filler selected from clay, activated zinc white, etc. to 100 parts by weight of silicon-terminated polyether.
Preferable results can be obtained if the amount is used in the range of 100 parts by weight. In addition, when it is desired to obtain a hardened composition with low strength and high elongation, fillers mainly selected from titanium oxide, calcium carbonate, magnesium carbonate, talc, ferric oxide, zinc oxide, and shirasu balloon are used. Favorable results can be obtained if the amount of 5 to 200 parts by weight is used per 100 parts by weight of silicon-terminated polyether. Of course, these fillers are 1
One type may be used alone or two or more types may be used in combination. In the present invention, it is more effective to use a plasticizer in combination with a filler because the elongation of the cured product can be increased and a large amount of filler can be mixed.
As the plasticizer, commonly used
For example, phthalate esters such as dioctyl phthalate, dibutyl phthalate, butylbenzyl phthalate; aliphatic dibasic acid esters such as dioctyl adipate, isodecyl succinate, dibutyl sebacate; and diethylene glycol dibenzoate, pentaerythritol ester, etc. Glycol esters; Aliphatic esters such as butyl oleate, methyl acetyl ricinoleate, etc.; Phosphate esters such as tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, etc.; Epoxidized soybean oil, benzyl epoxy stearate Epoxy plasticizers such as; plasticizers such as chlorinated paraffin alone or in combination
It can be used arbitrarily in the form of a mixture of more than one type. The amount of plasticizer is based on 100 parts by weight of silicon-terminated polyether.
Favorable results are obtained when used in a range of 0 to 100 parts by weight. The blended composition of the present invention further includes the optional use of additives such as adhesion promoters such as phenolic resins and epoxy resins, pigments, anti-aging agents, and ultraviolet absorbers. The compositions obtained in the present invention are 1 liquid and 2 liquid.
It is particularly useful as a liquid elastic sealant and can be used as a sealant for buildings, ships, automobiles, roads, etc. Furthermore, it can be used alone or with the aid of a primer to adhere to a wide range of substrates such as glass, porcelain, wood, metal, resin moldings, etc., and therefore can be used in various types of sealing compositions and adhesive compositions. . Furthermore, it is also useful as a food packaging material, a casting rubber material, a molding material, and a paint. Examples will be specifically described below. Production example 1 Allyl ether group (CH ₂ =
Contains 97% of CHCH ₂ O−) at the end,
800g of polypropylene oxide with an average molecular weight of 8000
Transfer to a pressure-resistant reaction vessel equipped with a stirrer.

Add 36 g of a silicon hydride compound having the structure [Formula], then add 0.34 ml of a chloroplatinic acid catalyst solution (a solution of 8.9 g of H ₂ PtCl ₆ 6H ₂ O dissolved in 18 ml of isopropyl alcohol and 160 ml of tetrahydrofuran). The mixture was reacted at 80°C for 6 hours. As a result of quantifying the residual hydrosilyl group from the IR spectrum, it was found that most of it had reacted. A polyether terminated with groups is obtained. Production Example 2 Allyl ether group (CH ₂ =
CHCH ₂ O−) 52%,

700 g of polypropylene oxide having an average molecular weight of 7,000 and containing 40% of [Formula] groups at the terminals is placed in a pressure-resistant reaction vessel equipped with a stirrer.

Add 46g of a silicon hydride compound having the structure of [Formula], then add 0.34ml of a catalyst solution of chloroplatinic acid (see Production Example 1) to 80%
The reaction was carried out at ℃ for 6 hours. The remaining hydrosilyl group
By quantifying with IR spectrum, it can be seen that almost no reaction occurs. at the end base and A polyether having the groups is obtained. Production Example 3 Allyl ether group (CH ₂ =
_CHCH2O− ) 48%

750 g of polypropylene oxide having an average molecular weight of 7500 and containing 45% of the groups at the terminals is placed in a pressure-resistant reaction vessel equipped with a stirrer.

76 g of a silicon hydride compound having the structure of [Formula] was added, followed by 0.7 ml of a catalyst solution of chloroplatinic acid (see Production Example 1), and the mixture was reacted at 80° C. for 10 hours. The remaining hydrosilyl group
By quantifying with IR spectrum, it can be seen that almost no reaction occurs. at the end base and A polyether having the groups is obtained. Production example 4 Allyl ether group (CH ₂ =
800 g of polypropylene oxide having an average molecular weight of 8000 and containing 97% of CHCH ₂ O-) at the terminal was placed in a pressure-resistant reaction vessel equipped with a stirrer.

Add 15.0 g of a compound having the structure [Formula], and then add a catalyst solution of chloroplatinic acid (H ₂ PtCl ₆ .
Add 0.34 ml of a solution of 8.9 g of 6H ₂ O dissolved in 18 ml of isopropanol and 160 ml of tetrahydrofuran,
The reaction was carried out at ℃ for 6 hours. The remaining hydrosilyl group
As a result of quantitative analysis from the IR spectrum, it was found that there was almost no reaction.

A polyether terminated with the group [Formula] was obtained. Reference Example 1 For 100 parts by weight of the silyl-terminated polyether of Production Example 1, 50 parts by weight of dioctyl phthalate, 110 parts by weight of calcium carbonate (Shiraishi Calcium CCR), 30 parts by weight of rutile titanium oxide, and carbon black.
0.5 parts by weight, 6 parts by weight of hydrogenated castor oil, 1 part by weight of 2,2'-methylene-bis-(4-methyl-6-ter-butylphenol), 2-(2'-hydroxy-
Add 1 part by weight of 3',5'-di-ter-butylphenyl)-5-chlorobenzotriazole, 3 parts by weight of tin octylate, and 1 part by weight of laurylamine, and obtain a well-mixed mixture using three paint rolls. . When this compound is left in the air at room temperature, it hardens overnight to become a rubber elastic body. Using a glass plate as an adherend and APZ-780 (manufactured by Nippon Unicar) as a primer, an H-shaped test piece was prepared in accordance with JISA5758.
After curing at 23°C and 55% temperature for 7 days, further curing at 50°C for 7 days, and performing a tensile test at a tensile speed of 50mm/min, the 150% modulus (M ₁₅₀ ) was 4.8Kg/
cm ² , strength at break (T _B ) of 9.2 Kg/cm ² , and elongation at break (E _B ) of 430%. Example 1, Comparative Example 1 As a plasticizer, 50 parts by weight of epoxyhydrophthalate (manufactured by Shin Nippon Rika, EPS) was used instead of 50 parts by weight of dioctyl phthalate, and 2 parts by weight was used instead of 8 parts by weight of tin octylate. A blend was prepared in exactly the same manner as in Reference Example 1 except for the use (Blend A Comparative Example 1). For 4 parts by weight of compound A30, 5
Parts by weight of dimethylpolysiloxane with silanol groups at both terminals (viscosity 3000 centistokes at 25°C) were added to prepare a well-mixed formulation (Formulation B).
Example 1). H-shaped test pieces were prepared using Compound B and Compound A in accordance with JISA5758, and a 9030 durability test was conducted. When we measured the recovery rate after the first compression process at 90℃ and 30%, we found that while compound A had a recovery rate of 50%, compound B had a recovery rate as high as 62%. The final durability results are also better with Formulation B than with Formulation A. Also, when a 3 mm thick sheet was made of Formulation A and Formulation B at 23°C and 50% humidity and cured for 7 days, there was some residual tack on the surface of the cured sheet of Formulation A (〇～△ level), whereas Formulation B
There is almost no residual tack on the surface of the sheet (level 0), which is an improvement. Comparative Examples 2 and 3 A blend was prepared in the same manner as in Example 1, except that the polyether obtained in Production Example 4 was used. (Formulations A and B) The measurement results of 9030 durability recovery rate and surface tack are shown in Table 1.

【table】 Reference example 2 For 303 parts by weight of the formulation of Reference Example 1,

Add 1.5 parts by weight of a silicon compound having the structure of [Formula] and mix well. An H-shaped test piece was prepared in the same manner as in Example 1,
After curing and tensile test, M ₁₅₀ 2.8Kg/cm ² ,
Results of T _B 7.3Kg/cm ² and E _B 620% are obtained. It can be seen that by adding the above silicone compound, a cured product with low modulus and high elongation can be obtained. Reference Examples 3 to 4 γ-Mercaptopropyltrimethoxysilane (Nihon Unicar A-189) or N-β-(aminoethyl)- was added to 804 parts by weight of the formulation of Reference Example 2.
0.5 parts by weight of each of γ-aminopropyltrimethoxysilane (A-1120 manufactured by Nippon Unicar) was added,
Mix well. An H-shaped test piece was prepared from the mixture in the same manner as in Reference Example 1, cured, and subjected to a tensile test. Table 2 shows the results.

[Table] Jurass products can be obtained.
For the formulations of Reference Examples 2, 3 and 4,
Anodized aluminum described in JISA5758 was used as the adherend, and an adhesion test was conducted using an H-type test piece without a primer. After curing for 7 days at 28°C and 50% humidity, a tensile test was performed, and the reference example 2 formulation had an E _B of only 80%, while the reference example 3 formulation had an E B of 220%. Reference example 4
The formulation had an E _B of 300%, an improvement. A-
It can be seen that the adhesion of the compound was improved by adding small amounts of 189, A-1120, etc. Reference Example 5 For 840 parts by weight of the silyl group-terminated polyether of Production Example 1,

Add 10 parts by weight of [Formula] (Ph is phenyl group), further add 0.4 parts of dibutyltin dilaurate, and under reduced pressure of 0.1 mmHg.
Heat treatment was carried out under stirring at 140°C for 10 hours. Except that 100 parts by weight of this heat-treated product was used instead of 100 parts by weight of the silyl-terminated polyether of Reference Example 1.
A compound was prepared in exactly the same manner as in Reference Example 1, cured, and subjected to a tensile test. M ₁₅₀ 3.5Kg/cm ² , T _B
A result of 8.5Kg/cm ² and _EB of 560% was obtained. It can be seen that the modulus is low and the elongation is high. Reference Example 6 A blend is prepared in exactly the same manner as in Reference Example 1, except that 100 parts by weight of the silyl-terminated polyether of Production Example 2 is used instead of 100 parts by weight of the silyl-terminated polyether of Production Example 1. When the compound was cured under the same conditions as Reference Example 1 and a tensile test was performed, T _B 6.8
Tensile property values of Kg/cm ² , E _B 660% were obtained. Reference Example 7 100 parts by weight of the silyl group-terminated polyether from Production Example 3 was used in place of 100 parts by weight of the silyl group-terminated polyether from Production Example 1, and 3 parts by weight of tin octylate and 1 part by weight of laurylamine as a condensation catalyst were used. A formulation is prepared in exactly the same manner as in Reference Example 1, except that 0.5 parts by weight of dibutyltin dilaurate is used instead. When the blend was cured and subjected to a tensile test under the same conditions as in Reference Example 1, tensile property values of T _B of 10.8 Kg/cm ² and E _B of 580% were obtained.

Claims (1)

[Claims] 1 (a) The following formula (Here, R〓 is a divalent organic group having 1 to 20 carbon atoms; R〓 is hydrogen or a monovalent organic group having 1 to 20 carbon atoms; R〓 is the same or different monovalent hydrocarbon group or Triorganosiloxy group; a is 0, 1,
2 or 3, b is 0, 1 or 2, c is 0 or 1, provided that 1a+b4; X is a different or similar hydrolyzable group; m is an integer selected from 0 to 18 have at one end,
The main chain essentially consists of chemically bonded repeating units represented by the following formula -R〓-O- (where R〓 is a divalent hydrocarbon group having 1 to 4 carbon atoms) with a molecular weight of 500 -200 parts by weight or less for 100 parts by weight of polyether of ~15,000, (b) the following formula (Here, R〓 is the same or different monovalent hydrocarbon group; n is a positive integer of 19 or more; d is 0, 1 or 2; Y is a hydroxyl group or the same or different hydrolyzable group. ) A room temperature curable composition comprising a diorganopolysiloxane represented by: 2. The room-temperature curable composition according to claim 1, wherein R〓 is a methylene group, R〓 is a hydride group, and the polyether is polypropylene oxide. 3. The room temperature curable composition according to claim 1, wherein the polyether has a molecular weight of 4,000 to 12,000. 4. The room temperature curable composition according to claim 1, wherein the diorganopolysiloxane is a liquid having a viscosity of 500,000 centistokes or less at 25°C. 5. A room-temperature curable composition according to claim 1, which uses a diorganopolysiloxane in which R〓 is a methyl group or a phenyl group, d=2, and Y is a hydroxyl group. 6. The room temperature curable composition according to claim 1, which uses diorganopolysiloxane in an amount of 50 parts by weight or less.