JP2023124211A - Bound stopper and manufacturing method thereof - Google Patents

Abstract

To provide a bound stopper having high mechanical strength and being easily manufactured.SOLUTION: In a bound stopper 10 formed of polyurethane foam, the polyurethane foam is obtained from a composition for polyurethane foam including at least an isocyanate component and a foaming agent, and the isocyanate component is an urethane prepolymer obtained from a composition including a polyol component and modified diphenylmethane di-isocyanate and having an isocyanate group at a terminal.SELECTED DRAWING: Figure 1

Description

The present invention relates to a bound stopper attached to a piston rod of a vehicle shock absorber and a method of manufacturing the same.

As shown in FIG. 9, a vehicle shock absorber 70 has a bound stopper 75 attached to a piston rod 72 of a cylinder. Reference numeral 71 denotes a cylinder body, and reference numeral 73 denotes a spring. The bound stopper 75 is made of an elastic foam molded into a bellows shape. When the shock absorber 70 expands and contracts due to impact or vibration from the road surface and the cylinder main body 71 collides with the bound stopper 75, the bound stopper 75 is compressed and deformed to generate an impact. mitigate

The bound stopper 75 is required to have high mechanical strength and endurance against fatigue failure and settling when repeatedly subjected to a large load because the cylinder body is repeatedly hit and compressively deformed due to the collision.

In the past, urethane raw materials with polyester-based polyol as the polyol component and diphenylmethane diisocyanate as the isocyanate component were injected into the mold as a bound stopper to reduce costs while providing durability and resistance to fatigue under high load and high deformation. , After performing primary vulcanization by heating at 70 ° C. or higher, by performing secondary vulcanization by removing the molded body from the mold and heating, the density (Da) and foam cell diameter (Ra) of the skin layer, It has been proposed that a polyurethane foam is formed so that the core density (Db) and foam cell diameter (Rb) satisfy specific formulas and relationships (Patent Document 1).

JP 2015-183832 A

However, primary vulcanization and secondary vulcanization allow the density (Da) and foam cell diameter (Ra) of the skin layer and the density (Db) and foam cell diameter (Rb) of the core portion to satisfy specific formulas and relationships. Therefore, it is difficult to control the reaction.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bound stopper that is excellent in mechanical strength and that is easy to manufacture, and a method for manufacturing the same.

A first aspect of the invention is a polyurethane foam bound stopper to be mounted on a piston rod of a vehicle shock absorber, wherein the polyurethane foam is obtained from a polyurethane foam composition containing at least an isocyanate component and a foaming agent. wherein the isocyanate component is an isocyanate group-terminated urethane prepolymer obtained from a composition containing a polyol component and modified diphenylmethane diisocyanate.

A second aspect of the invention is characterized in that, in the first aspect of the invention, the modified diphenylmethane diisocyanate is urethane-modified diphenylmethane diisocyanate and/or carbodiimide-modified diphenylmethane diisocyanate.

A third aspect of the invention is characterized in that, in the first or second aspect of the invention, the polyol component contains polytetramethylene ether glycol and/or polyester polyol.

A fourth aspect of the invention is that in any one of the first to third aspects of the invention, the urethane prepolymer having an isocyanate group at its terminal has an NCO% of 1.0 to 10.0%. Characterized by

According to a fifth aspect of the invention, in any one of the first to fourth aspects of the invention, the density is 0.2 to 0.9 g/cm ³ or the tensile strength is 3.0 MPa or more. .

A sixth aspect of the invention is a method for producing a bound stopper made of polyurethane foam to be attached to a piston rod of a vehicle shock absorber, wherein an isocyanate group obtained from a composition containing a polyol component and modified diphenylmethane diisocyanate is terminated. A polyurethane foam composition containing a urethane prepolymer and a foaming agent is injected into a mold and foamed to form the polyurethane foam bound stopper.

ADVANTAGE OF THE INVENTION According to this invention, the bound stopper which is excellent in mechanical strength and is easy to manufacture is obtained.

FIG. 4 is a cross-sectional view of a bound stopper according to one embodiment of the present invention; FIG. 4A is a cross-sectional view of a mold used to manufacture the bound stopper of the present invention and a cross-sectional view of the mold during foaming; FIG. 4 is a cross-sectional view of the mold at the time of demolding in manufacturing the bound stopper of the present invention; 4 is a table showing the contents of PO-1 to PO-6; 1 is a table showing formulations and physical properties of Examples 1-7. 1 is a table showing formulations and physical properties of Examples 8-12. 1 is a table showing formulations and physical properties of Examples 13-19. 2 is a table showing formulations and physical properties of Examples 20 to 27 and Comparative Example 1. FIG. It is a sectional view showing the mounting state of the bound stopper.

A bound stopper 10 according to an embodiment of the present invention shown in FIG. 1 is attached to a piston rod 72 of a shock absorber of a vehicle similarly to the bound stopper 75 shown in FIG.

The bound stopper 10 is made of a tubular polyurethane foam with a bellows-shaped side outer peripheral surface 10a, and has a through hole 11 in the center through which the piston rod of the shock absorber can be inserted. The bound stopper 10 is formed such that the upper portion 10b has a larger outer diameter than the lower portion 10c. The length and diameter of the bound stopper 10 are determined according to the shock absorber.

In the following, when an upper limit value and a lower limit value are separately described, a numerical range combining any upper limit value and any lower limit value is substantially disclosed.
The density of the polyurethane foam constituting the bound stopper 10 (in accordance with JIS K7222:2005) is 0.2 g/cm ³ or more, preferably 0.3 g/cm ³ or more. Further, it is preferably 0.9 g/cm ³ or less, 0.8 g/cm ³ or less, 0.7 g/cm ³ or less, and 0.6 g/cm ³ or less. The density can be 0.2-0.9 g/cm ³ . When the density is less than 0.2 g/cm ³ , the physical properties of the polyurethane foam deteriorate, and when the density exceeds 0.9 g/cm ³ , the foaming pressure increases during foam molding of the polyurethane foam. molding becomes difficult.

The tensile strength (JIS K6251:2017 compliant) of the polyurethane foam constituting the bound stopper 10 is 8.0 MPa or less, 7.0 MPa or less, and 6.0 MPa or less.

The polyurethane foam constituting the bound stopper 10 is obtained from a polyurethane foam composition. The polyurethane foam composition contains at least an isocyanate component and a blowing agent.

The isocyanate component is an isocyanate group-terminated urethane prepolymer obtained from a composition containing a polyol component and a modified diphenylmethane diisocyanate.

The polyol component may be either or both of polyether polyol and polyester polyol, but preferably contains polytetramethylene ether glycol (PTMG) and/or polyester polyol.

Polytetramethylene ether glycol (PTMG) has the following formula: [HO-(CH ₂ CH ₂ CH ₂ CH ₂ O) _n -H].

The polyester polyol is not particularly limited, but is preferably a polyester polyol having an average carbon number of 3 to 8 between ester bonds, more preferably a polyester polyol having an average carbon number of 5 to 8 between ester bonds. The average number of carbon atoms between ester bonds does not include the number of carbon atoms forming the ester bonds. Also, a plurality of polyester polyols may be used.

Condensed polyester polyols or ring-opened polyester polyols are used as polyester polyols having an average carbon number of 5 to 8 between ester bonds.
As the condensed polyester polyol, a polycondensation product of a diol having 4 to 6 carbon atoms between hydroxyl groups and a dicarboxylic acid having 4 to 10 carbon atoms between carboxyl groups is preferable.

Diols having 4 to 6 carbon atoms between hydroxyl groups include 1,4-butanediol [HO-(CH ₂ ) ₄ -OH] and 1,6-hexanediol [HO-(CH ₂ ) ₆ -OH]. can be mentioned.
Dicarboxylic acids having 4 to 10 carbon atoms between carboxyl groups include adipic acid [HOOC-(CH ₂ ) ₄ -COOH], suberic acid [HOOC-(CH ₂ ) ₆ -COOH], sebacic acid [HOOC-( CH ₂ ) ₈ -COOH], dodecanedioic acid [HOOC-(CH ₂ ) ₁₀ -COOH]. The number of carbon atoms between carboxyl groups does not include the number of carbon atoms constituting the carboxyl groups.

Polycaprolactone diol (PCL) obtained by ring-opening polymerization of ε-caprolactone is preferable as the polyester polyol.

The mixing ratio (weight) of polytetramethylene ether glycol (PTMG) and polycaprolactone diol (PCL) contained in the polyol component is preferably PTMG:PCL=100:0 to 10:90.

The polyol used preferably has a weight average molecular weight (Mw) of 800 to 5000, more preferably 1000 to 3000, and a hydroxyl value of 20 to 200 mgKOH/g, more preferably 35 to 180 mgKOH/g.

Modified diphenylmethane diisocyanate (modified MDI) is preferably liquid at room temperature, and examples thereof include urethane modified, carbodiimide modified, urea modified, burette modified and allophanate modified. Modified diphenylmethane diisocyanate, which is liquid at room temperature, has the advantage of being easy to handle without the need to heat-melt the polyisocyanate when producing a prepolymer having an isocyanate group at its terminal. Among liquid modified diphenylmethane diisocyanates, urethane-modified diphenylmethane diisocyanate (urethane-modified MDI) and carbodiimide-modified diphenylmethane diisocyanate (carbodiimide-modified MDI) are preferable. A plurality of modified diphenylmethane diisocyanates may be used.

By using the modified diphenylmethane diisocyanate, the brittleness of the polyurethane foam can be improved, the mechanical strength can be improved, and fatigue and fatigue failure when subjected to repeated heavy loads can be improved.

The NCO % (theoretical value) of the urethane prepolymer having terminal isocyanate groups is preferably 1.0 to 10.0%, more preferably 2.0 to 6.0%. If the NCO% is less than 1.0%, sufficient strength cannot be obtained and durability is also deteriorated. On the other hand, when the NCO% exceeds 10.0%, the flexibility decreases, the material becomes hard, the material becomes brittle, and the durability decreases.
The "NCO% (theoretical value)" in the urethane prepolymer having an isocyanate group at its terminal is the NCO% value obtained by calculation, and is calculated according to the following formula.
NCO% (theoretical value) = [(number of moles of NCO groups - number of moles of polyol) x NCO molecular weight] / [mixture amount of polyisocyanate + blend amount of polyol] x 100

The isocyanate group-terminated urethane prepolymer used in the present invention can be obtained by a known urethane prepolymer production method. Specifically, after a predetermined amount of polyol component is put into a tank or the like, it is heated to a predetermined temperature (for example, 130° C.), and while the heated temperature is maintained and nitrogen is filled, a predetermined amount of modified diphenylmethane diisocyanate is added while stirring. By charging and reacting, the urethane prepolymer having terminal isocyanate groups used in the present invention can be obtained. Further, when producing a urethane prepolymer having an isocyanate group at its terminal, along with the polyol component and the modified diphenylmethane diisocyanate, appropriate required components such as a cross-linking agent, a flame retardant, a coloring agent, etc. may be added to a tank or the like and mixed. good.

Blowing agents included in polyurethane foam compositions can be water, CFC alternatives, or hydrocarbons such as pentane, alone or in combination. In the case of water, carbon dioxide gas is generated during the reaction of the isocyanate component, and the carbon dioxide gas causes foaming. The blending amount of water as a blowing agent is preferably 0.2 to 5 parts by weight with respect to 100 parts by weight of the urethane prepolymer having an isocyanate group at its terminal.

The polyurethane foam composition may contain additives such as catalysts, foam stabilizers, anti-hydrolysis agents, cross-linking agents, flame retardants, colorants, stabilizers and fillers.

As the catalyst, a known urethanization catalyst or retardation catalyst (temperature-sensitive catalyst) can be used in combination. Examples of urethanization catalysts include amine catalysts such as triethylamine, triethylenediamine, diethanolamine, dimethylaminomorpholine, N-ethylmorpholine, and tetramethylguanidine; tin catalysts such as stannus octoate and dibutyltin dilaurate; and phenylmercuric propionic acid. Metal catalysts such as salts or lead octenoate (also referred to as organometallic catalysts) can be used. The retarded catalyst is an amine salt obtained by blocking the active group portion of the urethanization catalyst with an acid such as formic acid or octylic acid. can be mentioned.

The foam stabilizer may be one used for polyurethane foams, and may include silicone foam stabilizers, fluorine-containing compound foam stabilizers, and known surfactants. If the foam stabilizer is added during the production of the urethane prepolymer with an isocyanate group at its end, it will be dispersed evenly in the urethane prepolymer with an isocyanate group at its end, so that the foam stabilizing ability can be improved and the cells will be fine and uniform. A polyurethane foam with excellent properties can be obtained.

Examples of hydrolysis-resistant agents include carbodiimide compounds. In particular, when a polyester polyol is used as the polyol component, the hydrolysis resistance of the polyurethane foam can be improved by blending an anti-hydrolysis agent. Since the carbodiimide group has reactivity with the active hydrogen group, it is preferably blended together with the foaming agent when producing the polyurethane foam.

Cross-linking agents include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, glycerin, trimethylolpropane and the like. The cross-linking agent is preferably added at the time of production of the urethane prepolymer having an isocyanate group at the end, and can be uniformly dispersed in the urethane prepolymer by mixing with the polyol component or the like in a molten state.

Flame retardants include halogenated compounds such as polyvinyl chloride, chloroprene rubber, and chlorinated polyethylene; condensed phosphoric acid compounds such as phosphoric acid esters and halogenated phosphoric acid esters; organic compounds such as melamine resins and urea resins; and inorganic compounds such as aluminum hydroxide. The flame retardant can be uniformly dispersed in the urethane prepolymer if it is blended during production of the urethane prepolymer having an isocyanate group at its terminal.

Examples of coloring agents include pigments and dyes. The colorant can be uniformly dispersed in the urethane prepolymer if it is blended during production of the urethane prepolymer having an isocyanate group at its terminal.

Examples of stabilizers include antioxidants, ultraviolet absorbers, light stabilizers, and the like. The stabilizer can be uniformly dispersed in the urethane prepolymer if it is blended during production of the urethane prepolymer having an isocyanate group at its terminal.

The isocyanate index (INDEX) is preferably 80-150, more preferably 90-140. When the isocyanate index is less than 80, the degree of cross-linking is small, and the polyurethane foam cannot obtain sufficient mechanical strength, and settling when subjected to repeated loads increases. , resulting in a stiffer or less elastic polyurethane foam. A more preferred isocyanate index is 95-135. The isocyanate index is an index used in the field of polyurethane foams, and is a numerical value representing the equivalent ratio of isocyanate groups to active hydrogen groups in the composition for polyurethane foams [equivalent of NCO group/equivalent of active hydrogen group × 100].

A method of manufacturing the bound stopper will be described. The production of the bound stopper consists of a process of producing a urethane prepolymer having an isocyanate group at its end, a process of injecting a polyurethane foam composition into a mold and foaming, and a demolding process.

In the process of producing a urethane prepolymer having an isocyanate group at its end, a predetermined amount of polyol component, a predetermined amount of modified diphenylmethane diisocyanate, and required components are heated to a predetermined temperature (e.g., 130°C) and stirred and mixed. Thus, a urethane prepolymer having an isocyanate group at its end is produced.

In the step of injecting and foaming the polyurethane foam composition into a mold, the polyurethane foam composition containing at least an isocyanate group-terminated urethane prepolymer, a foaming agent, and appropriate additives is placed in a mold. Inject and foam to form the polyurethane foam bound stopper.

FIG. 2(2-A) shows an embodiment of the bound stopper mold 30. As shown in FIG. The mold 30 consists of a lower mold 31 , a middle mold 33 and an upper mold 35 .
The lower mold 31 is composed of a first lower mold 31a and a second lower mold 31b that can be divided into left and right, and has mold surfaces 311a and 311b that form the side outer peripheral surface 10a of the bound stopper 10. As shown in FIG.
The intermediate die 33 is substantially rod-shaped and has a die surface 33a forming the through-hole 11 of the bound stopper 10 on its outer circumference, and is arranged between the first lower die 31a and the second lower die 31b. The lower mold 31 and the middle mold 33 form a cavity 34 between the mold surface 311a of the first lower mold 31a, the mold surface 311b of the second lower mold 31b, and the mold surface 33a of the middle mold 33 by combining them.

After injecting the polyurethane foam composition into the cavity 34, as shown in FIG. 2(2-B), an upper mold 35 is placed over the mold to close it, and the polyurethane foam composition 40 is reacted to foam. Let The mold is left in a closed state for a predetermined time for curing (primary curing) to form the bound stopper 10 made of polyurethane foam. The primary curing conditions are preferably 60 to 120° C. for 10 to 120 minutes.

In the demolding step, as shown in FIG. 3, the upper mold 35 is removed, the first lower mold 31a and the second lower mold 31b are opened, and the middle mold 33 is separated. The intermediate mold 33 separated from the first lower mold 31a and the second lower mold 31b is fitted in the through hole 11 of the bound stopper 10 made of the polyurethane foam. After that, the bound stopper 10 is extracted from the middle die 33 by utilizing its elasticity. It is preferable that the bound stopper 10 is subjected to secondary curing after demolding. The secondary curing conditions are preferably 90 to 180° C. for 8 to 24 hours.

<Preparation of urethane prepolymer having an isocyanate group at its end>
A urethane prepolymer having terminal isocyanate groups was prepared from the following polyol and polyisocyanate.

(polyol)
・PTMG-1
PTMG-1 is polytetramethylene ether glycol, Mw: 2000, bifunctional, hydroxyl value: 56 mgKOH/g, product number: PTMG2000, manufactured by Mitsubishi Chemical Corporation.
・PTMG-2
PTMG-2 is polytetramethylene ether glycol, Mw: 1000, difunctional, hydroxyl value: 112 mgKOH/g, product number: PTMG1000, manufactured by Mitsubishi Chemical Corporation.
・PTMG-3
PTMG-3 is polytetramethylene ether glycol, Mw: 3000, bifunctional, hydroxyl value: 37 mgKOH/g, product number: PTMG3000, manufactured by Mitsubishi Chemical Corporation.

・PO-1
PO-1 is composed of adipic acid (AA) with 4 carbon atoms between carboxylic acids and ethylene glycol (EG) with 2 carbon atoms between hydroxyl groups, with an average carbon number of 3 between ester bonds and repetition between ester bonds. Condensed polyester polyol with different units, Mw: 2000, Number of functional groups: 2, Hydroxyl value: 56 mgKOH/g, Product name: Polylite OD-X-102, manufactured by DIC.

・PO-2
PO-2 is composed of adipic acid (AA) with 4 carbon atoms between carboxylic acids and 1,4-butanediol (BG) with 4 carbon atoms between hydroxyl groups, with an average carbon number of 4 between ester bonds. It is a condensed polyester polyol in which repeating units between bonds are the same, Mw: 2000, Number of functional groups: 2, Hydroxyl value: 56 mgKOH/g, Product name: Polylite OD-X-668, manufactured by DIC.

・PO-3
PO-3 is composed of adipic acid (AA) with 4 carbon atoms between carboxylic acids and 1,6-hexanediol (HD) with 6 carbon atoms between hydroxyl groups, with an average carbon number of 5 between ester bonds. Condensed polyester polyol with different repeating units between bonds, Mw: 2000, Number of functional groups: 2, Hydroxyl value: 56 mgKOH/g, Product name: HS2H-201AP, manufactured by Toyokuni Oil Co., Ltd.

・PO-4
PO-4 has an average carbon number of 7 between ester bonds consisting of sebacic acid (SA) with 8 carbon atoms between carboxylic acids and 1,6-hexanediol (HD) with 6 carbon atoms between hydroxyl groups. Condensed polyester polyol with different repeating units between bonds, Mw: 2000, Number of functional groups: 2, Hydroxyl value: 56 mgKOH/g, Product name: HS2H-201AP, manufactured by Toyokuni Oil Co., Ltd.

・PO-5
PO-5 has an average carbon number of 8 between ester bonds consisting of dodecanedioic acid (DDA) with 10 carbon atoms between carboxylic acids and 1,6-hexanediol (HD) with 6 carbon atoms between hydroxyl groups; Condensed polyester polyol with different repeating units between ester bonds, Mw: 3700, Number of functional groups: 2, Hydroxyl value: 30 mgKOH/g, Product name: Polylite OD-X-2555, manufactured by Toyokuni Oil Co., Ltd.

・PO-6
PO-6 is a polycaprolactone diol (PCL) having an average carbon number of 5 between ester bonds obtained by ring-opening polymerization of ε-caprolactone and the same repeating unit between the ester bonds, Mw: 2000, number of functional groups: 2, Hydroxyl value: 56 mgKOH/g Product name: Plaxel 220, manufactured by Daicel.
The contents of polyols PO-1 to PO-6 are collectively shown in FIG.
(polyisocyanate)
・MP102
MP102 is urethane-modified diphenylmethane diisocyanate (urethane-modified MDI), NCO%: 23%, product name: Lupranate MP102, manufactured by BASF INOAC Polyurethanes.
・MM103
MM103 is carbodiimide-modified diphenylmethane diisocyanate (carbodiimide-modified MDI), NCO%: 30%, product name: Lupranate MM103, manufactured by BASF INOAC Polyurethanes.
・MDI
MDI is 4,4'-diphenylmethane diisocyanate (monomeric MDI), NCO%: 33.6%, solid at room temperature, product name: Millionate MT, manufactured by Tosoh Corporation.

Urethane prepolymers having terminal isocyanate groups were prepared as follows using the above polyols and polyisocyanates at the blending ratios of Examples 1 to 27 and Comparative Example 1 shown in FIGS.

Into a 20 L metal reaction vessel, the specified amounts of polyol and polyisocyanate in Examples 1A to 13A and Comparative Example 1A were charged, and after charging, heated at 130 ° C., stirred and mixed for 20 minutes, and then the reaction vessel was placed. A urethane prepolymer having an isocyanate group at its end (Liquid B) was produced by allowing it to stand at room temperature and slowly cooling it.

<Production of test piece>
Using the prepared urethane prepolymer (Liquid B) having an isocyanate group at its end and the following foaming liquid (Liquid A), test pieces of each Example and Comparative Example 1 were prepared by the method described later.
The foaming liquid (liquid A) contains a compound having an active hydrogen group shown below, a surfactant, and a catalyst.
The ratio of each component of the foaming liquid (liquid A) was 700:400:5 (compound having an active hydrogen group:surfactant:catalyst).
・ Compound having an active hydrogen group; Mixed liquid containing castor oil and water, Product number: Advade SV (weight ratio of castor oil and water 50:50), manufactured by Rhein Chemie Japan ・ Surfactant; Product name: Braunon O-200SA, Ito Manufactured by an oil refinery ・Catalyst; Product name: Product name: Adcat PP, Rhein Chemie Japan Co., Ltd.

A polyurethane foam composition was prepared by blending a urethane prepolymer having an isocyanate group at its terminal temperature-controlled to 80°C and a foaming liquid temperature-controlled to 40°C at the blending ratio of each Example and Comparative Example 1. was made. After the polyurethane foam composition was mixed, it was injected into a test piece mold whose temperature was controlled at 80° C. in amounts shown in FIGS. The test piece mold has a cavity of 200×110×30 mm. After the polyurethane foam composition was injected into the mold, it was foamed in the mold, cured at 80° C. for 30 minutes (primary cure), and then the resulting polyurethane foam was removed from the mold. After demolding, the polyurethane foam was further cured at 100° C. for 12 hours (secondary curing) to obtain test pieces for each of Examples and Comparative Example 1.

<Product production>
Using the product mold (cavity volume 152 ml) shown in FIGS. A product (bound stopper) of each example and comparative example 1 was obtained.

Density and tensile strength were measured for the test pieces of each Example and Comparative Example 1, and durability was measured for the product. Measurement results are shown in Figures 5 to 8.

The density was measured according to JIS K7222:2005 using a test piece (200×110×30 mm) as it was as a measurement sample (both upper and lower surfaces and side surfaces had skin layers).

Tensile strength was measured according to JIS K6251:2017 by slicing a No. 2 dumbbell x 2 mm thick measurement sample (no skin layer on all upper and lower surfaces and side surfaces) from the test piece. Tensile strength was judged as "x" when less than 3 MPa, and judged as "good" when it was 3 MPa or more.

In the durability measurement, the product (bound stopper 10) is inserted into the shaft, and the upper surface of the upper portion 10b and the lower surface of the lower portion 10c of the inserted product are sandwiched between disc-shaped plates and fixed. A load cell is installed on the upper surface of the disk-shaped plate at the top of the product, and a repeated test is performed by applying repeated compression to the product from the lower surface of the disk-shaped plate at the bottom of the product under the measurement conditions of 6 KN × 1 Hz, and cracks occur in the product. When the number of repeated compressions was less than 80,000 times, it was judged as "x";
Also, if there is an "x" in either the tensile strength judgment or the durability judgment, the overall judgment will be "x", if both judgments are "△" or if both judgments are "△" and "〇" The overall judgment was "△", and when both judgments were "◯", the overall judgment was "◯".

Examples 1 to 4 are a urethane prepolymer (NCO%: 3.1% to 6.0%) having an isocyanate group at its end, which was produced using PTMG-1 and MP102 (urethane-modified MDI), and a foaming liquid. A polyurethane foam composition was prepared so as to have the isocyanate index of each example, and injected into a test piece mold and a product mold to prepare a test piece and a product.
Examples 1 to 4 had a density of 0.50 g/cm ³ , a tensile strength of 3.8 to 5.0 MPa, a tensile strength judgment of “◯”, a durability judgment of “◯”, and a comprehensive judgment of “◯”. Ta.

Examples 5 to 7 used urethane prepolymers (NCO% 4.9 to 5.0%) having isocyanate groups at their ends, which were produced by using different polyols and using MP102 (urethane-modified MDI) as the polyisocyanate. For example. The polyol of Example 5 is PTMG-2, the polyol of Example 6 is PTMG-3, and the polyol of Example 7 is a 1:1 combination of PTMG-1 and PO-6 (PCL).
Examples 5 to 7 had a density of 0.50 g/cm ³ , a tensile strength of 4.2 to 5.2 MPa, a tensile strength evaluation of “◯”, a durability evaluation of “◯”, and an overall evaluation of “◯”. Met.

Examples 8 to 10 are examples in which the injection amounts to the test piece mold and the product mold were changed.
Examples 8-10 used an isocyanate-terminated urethane prepolymer (4.9% NCO) made with PTMG-1 and MP102 (a urethane-modified MDI).
Examples 8 to 10 have a density of 0.32 to 0.61 g/cm ³ , a tensile strength of 3.5 to 5.0 MPa, a tensile strength judgment of “◯”, and a durability judgment of “◯”. The judgment was "0".

In Example 11, PTMG-1 and PO-6 were used together as polyols at a ratio of 1:9, and polyisocyanate was MP102 (urethane-modified MDI). 9) is used.
In Example 11, the density was 0.50 g/cm ³ , the tensile strength was 4.2 MPa, the tensile strength evaluation was "◯", the durability evaluation was "◯", and the overall evaluation was "◯".

Example 12 is an example using an isocyanate group-terminated urethane prepolymer (NCO%: 3.1%) prepared using PTMG-1 and MM103 (carbodiimide-modified MDI).
In Example 12, the density was 0.50 g/cm ³ , the tensile strength was 3.5 MPa, the tensile strength was evaluated as "◯", the durability was evaluated as "◯", and the overall evaluation was "◯".

Examples 13 to 16 are isocyanate groups prepared using polyester polyols PO-3 (AA/HD) to PO-6 (PCL) having an average carbon number of 5 to 8 between ester bonds and MP102 (urethane-modified MDI) A polyurethane foam composition is prepared with a urethane prepolymer (NCO%: 5.0%) having a terminal and a foaming liquid so that the isocyanate index is 108, and a test piece mold and a product mold Molds were injected to produce test pieces and products.
Examples 13 to 16 have a density of 0.49 to 0.52 g/cm ³ , a tensile strength of 4.2 to 4.9 MPa, a tensile strength judgment of “◯”, a durability judgment of “◯”, and a comprehensive judgment of “ 0” was.

Examples 17 to 19 are examples in which the NCO% of the urethane prepolymer having an isocyanate group at the end was varied.
Examples 17 to 19 are urethane prepolymers having isocyanate groups at their ends (NCO%: 3.0-6.0%) was used.
Examples 17 to 19 have a density of 0.48 to 0.52 g/cm ³ , a tensile strength of 4.0 to 4.7 MPa, a tensile strength judgment of “◯”, a durability judgment of “◯”, and a comprehensive judgment of “ 0” was.

Examples 20 to 22 are examples in which the injection amounts to the test piece mold and the product mold were changed.
Examples 20 to 22 are urethane prepolymers having terminal isocyanate groups (NCO%: 5.0%) was used.
Examples 20 to 22 have a density of 0.32 to 0.61 g/cm ³ , a tensile strength of 4.0 to 4.5 MPa, a tensile strength judgment of “◯”, a durability judgment of “◯”, and a comprehensive judgment of “ 0” was.

Example 23 is an isocyanate group-terminated urethane prepolymer (NCO%: 5.0%) is used.
In Example 23, the density was 0.49 g/cm ³ , the tensile strength was 4.2 MPa, the tensile strength was judged as "◯", the durability was judged as "◯", and the overall judgment was "◯".

Example 24 is a urethane prepolymer having terminal isocyanate groups (NCO%: 5.0%) produced using polyester polyol PO-6 (PCL) having an average carbon number of 5 between ester bonds and MM103 (carbodiimide-modified MDI). 0%) is used.
In Example 24, the density was 0.50 g/cm ³ , the tensile strength was 4.4 MPa, the tensile strength was judged as "◯", the durability was judged as "◯", and the overall judgment was "◯".

Examples 25 and 26 are examples in which the isocyanate index was changed, and were produced using polyester polyol PO-1 (AA/EG) and MP102 (urethane-modified MDI) having an average carbon number of 3 between ester bonds. A urethane prepolymer (NCO%: 6.0%) having terminal isocyanate groups was used.

Example 25 is an example of an isocyanate index of 130, and has a density of 0.50 g/cm ³ , a tensile strength of 3.8 MPa, a tensile strength judgment of “◯”, a durability judgment of “△”, and an overall judgment of “△”. , and the tensile strength and durability were somewhat inferior to those of Examples using a polyester polyol having an average carbon number of 5 to 8 between ester bonds.

Example 26 is an example of an isocyanate index of 110, a density of 0.50 g/cm ³ , a tensile strength of 3.4 MPa, a tensile strength determination of “◯”, a durability determination of “◯”, and a comprehensive evaluation of “ 0” was.

Example 27 is a urethane prepolymer (NCO%: 5.0%) is used.
In Example 27, the density was 0.51 g/cm ³ , the tensile strength was 3.8 MPa, the tensile strength was judged to be “◯”, the durability was judged to be “△”, and the overall judgment was “△”. Tensile strength and durability were somewhat inferior to those of Examples using a polyester polyol having 5 to 8 carbon atoms.

Comparative Example 1 is a urethane prepolymer (NCO%4 .9%) is used.
Comparative Example 1 had a density of 0.50 g/cm ³ , a tensile strength of 2.9 MPa, a tensile strength evaluation of “×”, a durability evaluation of “×”, and an overall evaluation of “×”.

Thus, according to the present invention, the bound stopper has excellent mechanical strength and is easy to manufacture.
It should be noted that the present invention is not limited to the embodiments, and modifications can be made without departing from the gist of the invention.

10 bound stopper 30 mold 31 lower mold 33 middle mold 35 upper mold

Claims (6)

In the polyurethane foam bound stopper attached to the piston rod of the vehicle shock absorber,
Consists of a polyurethane foam obtained from a polyurethane foam composition containing at least an isocyanate component and a foaming agent,
The bound stopper, wherein the isocyanate component is a urethane prepolymer having terminal isocyanate groups obtained from a composition containing a polyol component and modified diphenylmethane diisocyanate. 2. The bound stopper according to claim 1, wherein said modified diphenylmethane diisocyanate is urethane-modified diphenylmethane diisocyanate and/or carbodiimide-modified diphenylmethane diisocyanate. 3. The bound stopper according to claim 1, wherein the polyol component contains polytetramethylene ether glycol and/or polyester polyol. The bound stopper according to any one of claims 1 to 3, wherein the urethane prepolymer having an isocyanate group at its end has an NCO% of 1.0 to 10.0%. The bound stopper according to any one of claims 1 to 4, characterized by having a density of 0.2 to 0.9 g/cm ³ and a tensile strength of 3.0 MPa or more. A method for manufacturing a polyurethane foam bound stopper to be attached to a piston rod of a vehicle shock absorber,
A polyurethane foam composition containing a urethane prepolymer having terminal isocyanate groups obtained from a composition containing a polyol component and modified diphenylmethane diisocyanate and a foaming agent is injected into a mold and foamed to form the polyurethane. A method of manufacturing a bound stopper, comprising forming a bound stopper made of foam.

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