JP7144939B2 - Automobile resin parts - Google Patents

Description

TECHNICAL FIELD The present invention relates to a resin member for automobiles, and more particularly to a resin member for automobiles with improved scratch resistance.

For example, in order to prevent the paint film from peeling off due to the rebounding of gravel when driving on rough roads, vinyl chloride-based chipping-resistant paint is applied to the lower part of the vehicle, or a urethane-based protective film is attached. It is

Japanese Patent Application Laid-Open No. 2004-115657 of Patent Document 1 discloses a protective film for automobile exterior having a film-like substrate made of an olefin elastomer having a modulus of elasticity of 45 to 65 MPa and an adhesive layer.

JP-A-2004-115657

However, the protective film described in Patent Document 1 requires the use of a hard film-like base material in order to facilitate the attachment work, and cannot sufficiently relax the stress caused by the collision of dust such as gravel, and has poor chipping resistance. Not enough.

In recent years, resin members (hereinafter referred to as resin members) have been adopted for the purpose of saving fuel by reducing weight, and resin members have come to replace not only metal materials but also glass. , can be used not only in the lower part of automobiles but also in visible places.

In particular, when a resin member is used as a substitute for glass, when abrasion scars occur, light scatters and becomes whitish, reducing visibility. should also be prevented from occurring.

The above-mentioned chipping scratches are so-called depression scratches and scratches caused by sharp dust such as gravel entangled in the brushes of a car wash machine or hitting a resin member due to splashing up while driving. Dust enters the resin member in the thickness direction due to a large amount of stress, and the surface of the resin member is gouged out.
Therefore, chipping scratches can be prevented by denting a wide range when a large stress is locally received from dust, dispersing the stress and relieving it, and preventing the dust from crawling into the resin member. .

On the other hand, wear scars, for example, when the resin member is wiped with a waste cloth or a car wash brush, the resin member receives a wide range of stress and becomes dented, and the dust interposed between the waste cloth or the car wash brush and the resin member is polished. It acts as an agent, moves on the surface of the resin member, and scratches widely and shallowly from the edge of the recess.
Therefore, by hardening the resin member so that the surface is not dented by the stress received over a wide range from waste cloths, car wash brushes, etc., the occurrence of abrasion scars is prevented by preventing the edges of the dents where abrasion scars are likely to occur. can be prevented.

However, if the resin member is hardened to prevent the occurrence of wear scars, the large local stress from the dust cannot be relieved, resulting in chipping scratches.

Since the resin member is generally a softer material than dust containing inorganic substances such as gravel, unlike inorganic materials such as glass which are harder than dust, both chipping scratches and abrasion scratches do not occur. It is difficult to prevent at the same time.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a resin member that can prevent the occurrence of both chipping scratches and abrasion scratches. be.

As a result of intensive studies in order to achieve the above object, the inventors of the present invention have found that the load-displacement curve of the entire resin member for automobiles varies linearly within the range of a predetermined amount of displacement. The present inventors have found that the above object can be achieved by adjusting and combining the hard coat layer and the hard coat layer, and have completed the present invention.

That is, the resin member for automobiles of the present invention is formed by directly laminating an elastomer layer and a hard coat layer in this order on a resin substrate,
The elastomer layer contains a thermoplastic elastomer and has a Shore A hardness of 85A to 98A and a thickness of 50 μm to 250 μm,
The hard coat layer is made of polyurethane resin or polymethyl methacrylate resin and has a thickness of 5 μm to 40 μm,
The resin member for automobile has a Martens hardness (HMT) of 10 to 40 N/mm ² , and the load (mN) and the displacement (μm) when a triangular pyramidal diamond indenter having a tip-to-edge angle of 115° is pushed. The relationship is characterized in that it satisfies the formula:

Inclination change amount ΔS<0.1 expression

However, in the formula, ΔS represents S2-S1.
S1 is the increase rate (slope) of the load when the displacement amount increases from 0.1 μm to 0.5 μm,
S2 is the rate of increase (inclination) of the load when the displacement increases from 0.5 μm to 1.0 μm.

According to the present invention, the elastomer layer and the hard coat layer are combined so that the load (mN)-displacement (μm) curve changes linearly when a predetermined indenter is pushed down to 1.0 μm. It is possible to provide a resin member that can prevent the occurrence of both chipping scratches and abrasion scratches that are different from each other.

It is a schematic sectional drawing of the resin member for motor vehicles. 4 is a load-displacement curve of the automotive resin member of Example 1. FIG. 4 is a load-displacement curve of the automotive resin member of Example 2. FIG. 10 is a load-displacement curve of the automotive resin member of Example 3. FIG. 4 is a load-displacement curve of the automotive resin member of Comparative Example 1. FIG. 5 is a load-displacement curve of the automotive resin member of Comparative Example 2. FIG. 10 is a load-displacement curve of the automotive resin member of Comparative Example 3. FIG. 10 is a load-displacement curve of the automotive resin member of Comparative Example 4. FIG.

The automobile resin member of the present invention will be described in detail.
The resin member for automobiles comprises an elastomer layer and a hard coat layer in this order on a resin substrate, and the elastomer layer contains a thermoplastic elastomer.
The load (mN)-displacement (μm) curve changes linearly when a triangular pyramidal diamond indenter (Triangular 115) having a tip-to-edge angle of 115° is pushed up to 10 μm.

Specifically, the relationship between the load (mN) and the amount of displacement (μm) satisfies the following formula.
Inclination change amount ΔS<0.1 expression where ΔS represents S2−S1.
The above S1 is
F0.1 is the load (mN) when the displacement amount is 0.1 μm (D0.1),
When the load (mN) when the displacement amount is 0.5 μm (D0.5) is F0.5,
(F0.5-F0.1)/(D0.5-D0.1),
Represents the rate of increase (slope) of the load when the amount of displacement increases from 0.1 μm to 0.5 μm,
The above S2 is
When the load (mN) when the displacement amount is 1.0 μm (D1.0) is F1.0,
(F1.0-F0.5)/(D1.0-D0.5),
It represents the rate of increase (inclination) of the load when the amount of displacement increases from 0.5 μm to 1.0 μm.

The resin member for automobiles has a hard coat layer on an elastomer layer, and is obtained by laminating a resin thinner and harder than the rubber-like elastic body on the rubber-like elastic body.

The stress from the dust that causes scratches is transmitted to the elastomer layer through the hard coat layer, so the shape of the load-displacement curve of the resin parts for automobiles can be adjusted by combining the elastomer layer and the hard coat layer. can be done.

Since the load-displacement curve is linear, the elastomer layer can reduce the reaction force against the stress from the dust, and the hard coat layer can reduce the amount of displacement due to the stress from the dust.

Therefore, when stress is applied locally, it displaces over a wide range to disperse the stress. It is possible to prevent the occurrence of both scratches and wear scars.

In other words, in general elastic deformation, as the amount of displacement increases, the reaction force increases and the amount of displacement against the load decreases. cannot be mitigated.

If the stress received from the dust is not relieved, the dust will creep into the automotive resin member in the thickness direction as described above, gouging the surface and causing chipping flaws.

If the elastic modulus is reduced to reduce the reaction force in order to prevent the above-mentioned chipping damage, it will become dented even when it is subjected to a wide range such as when it is wiped with a waste cloth or a car wash brush. As described above, abrasion marks are generated by scraping off from the edge of the recess.

Therefore, in general elastic deformation as described above, it is difficult to prevent both chipping scratches and wear scratches, but the linear load-displacement curve enables stress dispersion and dent prevention. can be compatible, and both chipping scratches and abrasion scratches can be prevented.

The load-displacement curve of the resin member for automobiles of the present invention shows the rate of increase (slope) of the load when the amount of displacement is from 0.1 μm to 0.5 μm, and the increase of the load when the amount of displacement is from 0.5 μm to 1.0 μm. The ratio (slope) is preferably 0.55 to 1.00 (mN/μm), more preferably 0.8 to 1.00 (mN/μm).
By keeping the rate of increase (slope) of the load within the above range, it is possible to prevent the occurrence of both chipping scratches and abrasion scratches.

Further, the automotive resin member has a Martens hardness (HMT) of 10 to 40 N/mm ² , preferably 15 to 25 N/mm ² .
If the Martens hardness is less than 10 N/mm ² , it is too soft and wear scars are likely to occur, and if it exceeds 40 N/mm ² , it is too hard and chipping scars are likely to occur. When the Martens hardness is 10 to 40 N/mm ² , the occurrence of both chipping scratches and abrasion scratches can be prevented.

The Martens hardness of the resin member for automobiles can be adjusted by combining the elastomer layer and the hard coat layer in the same manner as the shape of the load-displacement curve.
Specifically, even if the hard coat layer is the same, softening the elastomer layer increases the displacement against load and lowers the Martens hardness. Increases hardness.

In the present invention, the Martens hardness (HMT) of the automotive resin member was measured under the following conditions in accordance with the method for measuring Martens hardness in ISO 14577-1 "Instrumented indentation hardness test".

The measurement device is a dynamic ultra-micro hardness tester DUH-211S manufactured by Shimadzu Corporation, and the indenter is Triangular 115. In the load-unload test mode, the test force is 1 mN, the minimum test force is 0.002 mN, the load speed is 3.0 mN/sec, the load The holding time was 5 sec, the unloading holding time was 10 sec, and the test temperature was 23°C.

<Elastomer layer>
The elastomer layer is deformed by stress from dust to relieve the stress, and the Shore A hardness of the elastomer layer is preferably 85A to 98A.
If the Shore A hardness is less than 80A, it is too soft and wear scars are likely to occur, and if it exceeds 98A, it is too hard and chipping scratches are likely to occur.

The Shore A hardness was measured using a type A durometer according to JIS K 6253-3 "Vulcanized rubber and thermoplastic rubber-Determination of hardness-Part 3: Durometer hardness".

The thickness of the elastomer layer affects the shape of the load-displacement curve and the Martens hardness (HMT) of the resin parts for automobiles because the stress from the dust is transmitted to the resin base material and the elastomer layer deforms indefinitely. Although there is no particular limitation as long as the thickness is not required, the practical upper limit is about 1.5 mm because the cost increases if the thickness is too large.

When a resin member is used as a substitute for glass, the thickness is preferably 50 μm to 250 μm, more preferably 70 μm to 200 μm.
If the elastomer layer is too thick, the transparency tends to be reduced, and the thickness tends to vary, which tends to cause optical distortion, which tends to lower the optical performance.

The elastomer layer contains a thermoplastic elastomer.
Since the elastomer is thermoplastic, it can be directly fused to a resin base material, which will be described later, and does not require an adhesive. In addition, there is no need to improve the attachment workability, and the degree of freedom in design is high.

As the thermoplastic elastomer, it is possible to select and use an elastomer that has affinity with the resin base material and the hard coat layer and that can be adhered.

Examples of the thermoplastic elastomer include urethane-based thermoplastic elastomers, styrene-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyester-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, and olefin-based rubber components. Mixtures, copolymers, and thermoplastic elastomers obtained by blending a thermoplastic resin and a kneadable rubber component can be used.
Among them, thermoplastic polyurethane elastomers are flexible and tough elastomers, and are excellent in moldability, transparency, and weather resistance, so they can be preferably used for automobile exterior parts and the like.

<Hard coat layer>
The hard coat layer is a resin layer that is thinner and harder than the elastomer layer, and is formed on the surface of the automotive resin member.

The thickness of the hard coat layer is preferably 5 μm to 40 μm, depending on the type of resin constituting the hard coat layer and the hardness of the elastomer.
By having a thickness within the above range, it is possible to disperse the locally received stress over a wide range and transfer it to the elastomer layer, and to prevent denting against the widely received stress.

Further, the hard coat layer preferably has a pencil hardness of B to 2H.
When the pencil hardness is less than B, the hard coat layer itself is too soft and easily damaged, and it may be difficult to transmit stress to the elastomer and may be easily damaged. It can get easier.

The pencil hardness was measured according to the scratch hardness (pencil method) of JIS K 5600-5-4 “General test methods for paints-Test methods for mechanical properties of coating films”.

As the resin constituting the hard coat layer, conventionally known resins used for automobile coating can be used.
Examples of the resins include polyurethane resins, acrylic resins, polyester resins, silicon-modified polyester resins, silicon-modified acrylic resins, alkyd resins, vinyl chloride resins, fluorine resins, and melamine resins.
Among them, polyurethane resins and polymethyl methacrylate resins are preferably used because of their toughness and excellent transparency.

<Production of automobile resin parts>
The above resin member for automobiles can be produced by producing a composite in which an elastomer layer is laminated on a resin base material, and coating and drying the hard coat layer coating liquid.

The above-mentioned composite is produced by forming a resin base material, layering a sheet-like elastomer, and fusing the elastomer to the resin base material by hot pressing, or forming a molten resin base material from two extruders. It can be produced by extruding and laminating a resin and a thermoplastic elastomer, followed by press molding.
It is also possible to mold by injecting the resin forming the resin base material in a molten state and the thermoplastic elastomer into a mold by a two-color injection method or a two-color injection press method.

The resin member for automobiles can be used for automobile glazing parts, resin exterior parts, resin interior trim parts, and the like.

Automotive glazing parts include window glass such as rear quarter windows, rear side windows, rear windows, sunroofs, and headlamp covers.
Examples of resin exterior parts include side mirror housings, bumpers, front grills, rear spoilers, side sill spoilers, and resin fenders.
In addition, resin interior trim parts include meter covers, center console covers, navigation covers, lamp covers, door trims, map lamps, center consoles, body side trims, luggage trims, tonneau covers, floor boards, instrument panels, and glove boxes. etc. can be mentioned.

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

<Preparation of resin substrate>
A polycarbonate resin (LEXAN: LS2-111: manufactured by Sabic) was injection molded using an injection molding machine (TM130F2: manufactured by Toyo Machinery & Metal Co., Ltd.) under the following conditions.

Regarding the molding temperature, the temperature at the tip of the nozzle of the injection molding machine was set at 300°C, the temperature of each cylinder was lowered by 5°C toward the hopper side, and the temperature at the bottom of the hopper was set at 285°C. The mold temperature was set at 90°C.
Polycarbonate resin is heated and melted, injected with a 40 mmφ screw at an injection speed of 80% (88 mm/sec) and an injection pressure of 90 Kgf/(1130 Kgf/cm ² ), and held at 80 Kgf/(1070 Kgf/cm ² ) for 15 seconds to obtain a thickness. A 2 mm thick plate-shaped resin substrate was obtained.

[Example 1]
A non-yellowing thermoplastic polyurethane elastomer (Elastollan: NY585A: manufactured by BASF; hardness 85A) using an aliphatic isocyanate was molded under the following conditions using an extruder (Plastogaph EC Plus, 19 mmφ).

The temperature at the nozzle tip of the extruder was set at 195°C, and the temperature at the bottom of the hopper was set at 180°C by decreasing the temperature of each cylinder by 5°C toward the hopper side.
The molten thermoplastic polyurethane elastomer was extruded through a T-shaped flat die of an extruder at a screw rotation speed of 10 to 15 rpm, and the take-up speed was adjusted to obtain a sheet-like elastomer having a thickness of 200 μm.

The sheet-like elastomer is placed on the resin base material, and the sheet-like elastomer is heated at 120° C. under a reduced pressure of 100 kPa using a vacuum press (manufactured by Mikado Equipment Sales Co., Ltd.) to soften it. A pressure of 5 kN was applied for 1 minute to heat-seal the sheet-shaped elastomer and the resin substrate, thereby forming an elastomer layer on the resin substrate.

Next, after applying a clear coat (PU High Gloss Clear: GF54055A PU SB HG CC: manufactured by BASF) to the elastomer layer to adjust the film thickness, it was cured in a hot air oven to form a hard coat with a film thickness of 30 μm. A layer was formed to obtain an automobile resin member.

FIG. 2 shows the load (mN)-displacement (μm) curve of the automotive resin member of Example 1. As shown in FIG.
The slope (S1) when the displacement amount is from 0.1 μm to 0.5 μm is 0.853,
The slope (S2) when the displacement amount is from 0.5 μm to 1.0 μm is 0.905,
ΔS was 0.052.
For S1 and S2, Martens hardness was measured five times, and the slopes of the respective load-displacement curves were averaged to obtain S1 and S2.

[Example 2]
An automotive resin member was obtained in the same manner as in Example 1, except that the thickness of the hard coat layer was 10 μm.

FIG. 3 shows the load (mN)-displacement (μm) curve of the automotive resin member of Example 2. As shown in FIG.
The slope (S1) when the displacement amount is from 0.1 μm to 0.5 μm is 0.561,
The slope (S2) when the displacement amount is from 0.5 μm to 1.0 μm is 0.602,
ΔS was 0.041.
[Example 3]
A non-yellowing thermoplastic polyurethane elastomer (Elastollan: NY998: manufactured by BASF; hardness 98A) using an aliphatic isocyanate was molded under the following conditions, and the thickness of the hard coat layer was set to 10 μm. An automobile resin member was obtained in the same manner as in Example 1.

The temperature at the nozzle tip of the extruder was set at 205°C, and the temperature at the bottom of the hopper was set at 190°C by decreasing the temperature of each cylinder by 5°C toward the hopper side.
The molten thermoplastic polyurethane elastomer was extruded through a T-shaped flat die of an extruder at a screw rotation speed of 10 to 15 rpm, and the take-up speed was adjusted to obtain a sheet-like elastomer having a thickness of 100 μm.

FIG. 4 shows the load (mN)-displacement (μm) curve of the automotive resin member of Example 3. As shown in FIG.
The slope (S1) when the displacement amount is from 0.1 μm to 0.5 μm is 0.848,
The slope (S2) when the displacement amount is from 0.5 μm to 1.0 μm is 0.838,
ΔS was −0.010.

[Comparative Example 1]
An automotive resin member was obtained in the same manner as in Example 2, except that the thickness of the elastomer layer was 100 μm.

FIG. 5 shows the load (mN)-displacement (μm) curve of the automotive resin member of Comparative Example 1. As shown in FIG.
The automotive resin member of Comparative Example 1 was destroyed when the displacement amount exceeded 0.15 μm, so ΔS could not be measured.

[Comparative Example 2]
An automobile resin member was obtained in the same manner as in Example 2, except that the elastomer layer was not formed.

FIG. 6 shows the load (mN)-displacement (μm) curve of the automotive resin member of Comparative Example 2. As shown in FIG.
The automobile resin member of Comparative Example 2 was destroyed when the displacement amount was around 0.20 μm, so ΔS could not be measured.

[Comparative Example 3]
An automobile resin member was obtained in the same manner as in Example 3, except that the elastomer layer was not formed.

FIG. 7 shows the load (mN)-displacement (μm) curve of the automotive resin member of Comparative Example 3. As shown in FIG.
The slope (S1) when the displacement amount is from 0.1 μm to 0.5 μm is 0.549,
The slope (S2) when the displacement amount is from 0.5 μm to 1.0 μm is 0.663,
ΔS was 0.114.

[Comparative Example 4]
An automobile resin member was obtained in the same manner as in Example 2, except that the hard coat layer was not formed.

FIG. 8 shows the load (mN)-displacement (μm) curve of the automobile resin member of Comparative Example 4. As shown in FIG.
The slope (S1) when the displacement amount is from 0.1 μm to 0.5 μm is 0.550,
The slope (S2) when the displacement amount is from 0.5 μm to 1.0 μm is 0.850,
ΔS was 0.300.

[Reference example 1]
Silicon dioxide (SiO ₂ ) was plasma-coated on the resin substrate to form a 0.01 μm glass coat layer.

<Evaluation>
Examples 1 to 3, Comparative Examples 1 to 4 Automotive resin members, and the glass-coated member of Reference Example 1 were tested by the following methods. Table 1 shows the evaluation results.
The pencil hardness of the hard coat layer was obtained by measuring the automobile resin member of Comparative Example 4 to obtain the pencil hardness of the hard coat layer.

(Car wash machine test)
Place the test piece on a black plate, measure the L value at an incident angle of 0 ° and a light receiving angle of 10 °, and compare it with the L value before the car wash machine test performed under the following conditions. was measured, and the scratch resistance was examined by light scattering.

As a car wash machine brush, the material used was polyethylene, the shape was a cross tip split type, and the total length of the brush was 220 mm.
The brush rotation speed and time were 150 rpm for 10 seconds.
The amount of water was 4 L/min.
The muddy water was a mixture of 8 types of test dust (JIS Z 8901):ion-exchanged water:0.75 wt % aqueous solution of sodium polyoxyethylene lauryl ether sulfate=3:10:2 (weight ratio).

The test surface of a test piece having dimensions of 70×30 mm was turned upward, and after dripping a specified amount (24±5 mmg·cm ² ) of muddy water, it was spread to 70×30 mm with a brush.
The test piece to which the muddy water was applied was placed at a distance of 150 mm from the center of the car wash brush, and the brush was rotated under specified conditions for a specified time while pouring a specified amount of water on the test piece.
Taking this as one cycle, after performing 167 cycles, the muddy water on the surface was removed, and a double-sided flannel (fabric raised on both sides) was wiped with alcohol in the scratch direction to remove brush scum.

(Peeling test)
The adhesion between the resin base material and the elastomer layer was measured by the following method before and after the weather resistance test.
According to JIS K 5600-5-6 "General test method for paint", draw 11 orthogonal vertical and horizontal parallel lines reaching the base material with a cutter knife at approximately the center of the test piece at intervals of 2 mm, and 100 squares. A grid-like cell was made.
Cellophane tape (registered trademark) with a width of about 18 mm to 30 mm was adhered to the grid-shaped test piece, and it was peeled off at once. 50% or more were regarded as acceptable cells, and those in which all 100 cells were acceptable were regarded as no peeling.

(weather resistance test)
A weather resistance test was carried out according to JIS K7350-2 using a weather resistance tester (ATLAS Ci400) manufactured by Toyo Seiki Co., Ltd.
Irradiation intensity: 60 W/m ² (wavelength range: 300 to 400 nm), black panel temperature: 63° C.±3° C. A test piece was subjected to accelerated deterioration.
One cycle was set to 120 minutes, and 500 cycles of spraying ion-exchanged water were performed for the first 12 minutes. The peel test was performed on the test piece after the weather resistance test.

The automotive resin member of Example 1 had a linear load (mN)-displacement (μm) curve and was excellent in scratch resistance. is large and the reaction force increases as the amount of displacement increases, so the stress from the dust cannot be relieved and the scratch resistance is poor.

In addition, it was confirmed that the automobile resin members of Examples 1 to 3 had ΔL of 4 or less before and after the car wash machine test, suppressed whitening due to light scattering, and had excellent scratch resistance.
In particular, the automotive resin members of Examples 1 and 3, which had a Martens hardness of 15 to 25 N/mm ² , had almost the same scratch resistance as the member of Reference Example 1 having a glass coat layer formed thereon.
The member of Reference Example 1 has high Martens hardness and scratch resistance, but requires plasma treatment and is very expensive.

REFERENCE SIGNS LIST 1 resin substrate 2 elastomer layer 3 hard coat layer

Claims (5)

A resin member for automobiles comprising an elastomer layer and a hard coat layer directly laminated in this order on a resin base material,
The elastomer layer contains a thermoplastic elastomer and has a Shore A hardness of 85A to 98A and a thickness of 50 μm to 250 μm,
The hard coat layer is made of polyurethane resin or polymethyl methacrylate resin and has a thickness of 5 μm to 40 μm,
The resin member for automobile has a Martens hardness (HMT) of 10 to 40 N/mm ² , and the load (mN) and displacement (μm) when a triangular pyramidal diamond indenter having a tip-to-edge angle of 115° is pushed. A resin member for automobiles, wherein the relationship satisfies the following formula.

Inclination change amount ΔS<0.1 expression

However, in the formula, ΔS represents S2-S1.
S1 is the rate of increase in load when the amount of displacement increases from 0.1 μm to 0.5 μm,
S2 is the rate of increase in load when the amount of displacement increases from 0.5 μm to 1.0 μm.
2. The automotive resin member according to claim 1 , wherein the automotive resin member has a Martens hardness (HMT) of 15 to 25 N/mm ² . 3. The resin member for automobiles according to claim 1 , wherein the elastomer layer has a thickness of 70 μm to 200 μm. The resin member for automobiles according to any one of claims 1 to 3 , wherein the elastomer layer contains a thermoplastic polyurethane elastomer. 5. The resin member for automobiles according to claim 1 , wherein the hard coat layer has a pencil hardness of B to 2H.

Images