Cavity sealing system for motor vehicle

Abstract

The present invention generally relates to a system for sealing a cavity of a motor vehicle frame, wherein a wall is associated with a motor vehicle structure; and prior to expansion of the expandable material, the expandable material is arranged by the extruder on and in contact with at least a portion of the wall, where the expandable material has an expansion rate of at least 400% when exposed to elevated temperatures typically used for the vehicle frame during production of the motor vehicle, and the expandable material has an expansion rate of at least 40% when exposed to elevated temperatures typically used for the vehicle frame during production of the motor vehicle. And wherein the expandable material is dry at ambient temperature before and after it is disposed to the wall.

Description

Technical Field

[0001] This invention generally relates to a cavity seal, for example, for improving sound absorption in motor vehicles, for improving vehicle rigidity, and / or for preventing unwanted components such as air, dust, and / or moisture from entering the vehicle frame. More specifically, this invention relates to the vehicle body of a motor vehicle in a white system. Background Technology

[0002] The transportation industry continues to require methods of insulation, reinforcement, and sealing that provide improved functionality while reducing weight and cost. One technique to mitigate these issues is the use of baffle structures, which, within cavities in the main body of a white structure, effectively block sound transmission through metal plate cavities and / or prevent unwanted components such as air, dust, and / or moisture from entering the frame. However, there remains a need for further noise reduction and / or increased frame rigidity, and / or further reduction of unwanted components such as air, dust, and / or moisture entering the frame.

[0003] Therefore, the problem of the present invention is to provide an improved system for sealing cavities in a motor vehicle frame. Summary of the Invention

[0004] This problem is solved by a system for sealing cavities in a vehicle frame, the system comprising: (a) walls associated with the structure of a motor vehicle; and (b) Expandable material disposed on at least a portion of the wall and in contact with the wall by an extruder before expansion. Wherein, when exposed to the high temperatures typically used for vehicle frames during motor vehicle production, the expansion rate of the expandable material is ≥400%, preferably ≥800% or >800%, more preferably ≥1000%, and wherein the expandable material is dry at ambient temperature before and after it is arranged on the wall.

[0005] This invention relates to the sealing of cavities, particularly the sealing of cavities in the body of a motor vehicle with a white structure, such as roof beams and strut structures. The system typically employs a substrate, a portion of which is preferably coated with an expandable material, and particularly a thermally activated resin expandable material, by extrusion. Preferably, the expandable material is provided as granules, which are extruded. At the outlet of the extruder, the expandable material is provided as beads, which are applied directly to the wall. For this application, the extruder and / or the wall move relative to each other.

[0006] An expandable material is applied to the wall of a motor vehicle structure using an extruder. Preferably, the extruder is connected to a robot that moves the extruder relative to the wall. The application can be supported by a visualization device, such as a camera, which takes photographs of the applied beads of expandable material. An additional computer system can analyze whether the expandable material is in the correct position and / or has the correct shape.

[0007] Preferably, the expandable material is dry at ambient temperature (approximately 20°C) before and after its application to the wall, and before it expands, meaning that the expandable material can be processed and / or the components can be stacked without sticking together.

[0008] In a particularly preferred embodiment, the substrate is the inner wall of a metal, plastic, or composite body component, and is partially coated with a thermally activated polymer, such as a moldable hot melt adhesive-based polymer or an expandable structural foam, examples of which include olefin polymers, vinyl polymers, polymers containing thermoplastic rubber, epoxy resins, urethanes, etc.

[0009] According to the invention, the expansion rate of the expandable material is at least 400%, preferably at least 800%, more preferably at least 1000% or even higher. This ensures that the structure is properly sealed against unwanted components such as air, dust, and / or moisture, improving noise reduction and / or improving the structural characteristics of the frame. The expansion of the expandable material is utilized at high temperatures, which are typically supplied to the frame during motor vehicle production (e.g., during electrophoresis or when the frame is coated with color).

[0010] In a preferred embodiment, an expandable material is placed on or near one or more inner walls that define cavities within a white motor vehicle body, such as roof rails, struts, rocker arms, or others. The expandable material is activated to achieve a polymer transformation (e.g., expansion or flow) within the cavity.

[0011] Preferably, the wall defines a cavity in the white body of a motor vehicle. More preferably, the wall is the inner wall surface of a vehicle pillar.

[0012] Preferably, the expandable material is a thermally activated thermoplastic foamable material.

[0013] More preferably, the expandable material is an acoustic polymer, a structural polymer, and / or a sealing polymer.

[0014] Preferably, the wall includes an exposed surface.

[0015] According to a preferred embodiment of the present invention, the wall is the inner wall of a hollow structural member.

[0016] Preferably, the wall is a vehicle body panel or a reinforcing component.

[0017] Preferably, the adhesion between the wall and the expandable material is between 0.25 and 1.5 N / mm. 2 Preferably 0.5 to 1 N / mm 2 This depends on the condition of the surface and the material of the wall.

[0018] The present invention has the following advantages: -Automatic application of expandable materials replaces manual operation, making it cheaper and more reliable. - The material is provided in granular form before extrusion, making it easy to handle. - This system does not require forming hard-to-obtain holes in the wall, such as when the wall is made of high-strength steel, or when holes could make the wall weak and extend into the vehicle structure.

[0019] The expandable material is preferably a hot melt adhesive formulation, including: (i) one or more solid polymers (ii) Thixotropic fillers (iii) Foaming agent system (iv) Crosslinking system, including - The first crosslinking agent, whose activation temperature is within the temperature range where the adhesive is heated to the foaming temperature, increases the melt viscosity of the adhesive to the temperature during the baking stage, and - A second crosslinking agent, whose activation temperature is within the foaming temperature range, to crosslink the foaming formulation.

[0020] After application, the adhesive is heated to a temperature range referred to herein as the cyclic baking stage. This invention reduces the likelihood of the adhesive sagging and potentially falling off the substrate due to adhesive failure during this stage.

[0021] The adhesive wets the surface to which it is applied, which improves the absorption of any oil and other contaminants on the surface, thereby improving adhesion, and a low melt viscosity is required here.

[0022] Therefore, the adhesive formulation of the present invention allows for the application of the adhesive to a substrate at one location to provide a substrate supporting a non-adhesive, heat-activated adhesive. If desired, the substrate can be transported to a second location where it can be assembled and subjected to a baking cycle heating system to induce foaming and development of adhesive properties. Using the adhesive of the present invention has the advantage of reducing the likelihood of adhesive failure between the adhesive and the substrate during the cyclic baking phase.

[0023] This is particularly useful in industries such as the automotive, railroad, and aircraft industries, where components, such as sheet metal, are prepared in one location and transported to another location for assembly. The adhesive is also particularly suitable for appropriate extrusion applications, such as those described in U.S. Patent Publication 2006 / 0127584, where the adhesive can be applied in one location using the described techniques and then transported elsewhere.

[0024] The presence of a first crosslinking agent and a thixotropic filler allows the formulation to be applied, for example, by melt coating, such as by extrusion at low melt viscosity while maintaining its shape to adhere to a surface with sufficient strength, and to remain dry upon cooling and to maintain its adhesion and shape to the substrate during the baking stage. The activation temperature of the first crosslinking agent is preferably 80°C-150°C, more preferably 100°C-130°C. It is also preferred that the first crosslinking agent has a relatively short half-life within this temperature range.

[0025] The adhesive is formulated and foamed at a temperature higher than that at which it is applied to the substrate. Therefore, the second crosslinking agent, activated at the higher foaming temperature, will be activated during the foaming stage to increase viscosity, retain the gas generated by the foaming agent, and provide strength to the foamed structure. The activation temperature of the second crosslinking agent is preferably 130°C-220°C, more preferably 140°C-180°C, and it has a longer half-life at temperatures within the activation range of the first crosslinking agent.

[0026] The polymers used in this invention are preferably copolymers (and terpolymers) of ethylene. In particular, unsaturated esters such as vinyl esters and acrylic and methacrylate esters are effective. As used herein, the term "copolymer" refers to a polymer of two or more monomers. Particularly preferred are ethylene / acrylate copolymers, and more particularly, copolymers of ethylene and butyl acrylate (preferably n-butyl acrylate). Examples of polymers that can be used include: (i) Ethylene-vinyl acetate copolymer (ii) Ethylene-methyl acrylate copolymer (iii) Ethylene-butyl acrylate copolymer (iv) Ethyl ethylene-2-hexyl acrylate copolymer (v) Polyamide polymers (vi) Glycidyl methacrylate, acrylate, ethylene copolymers (vii) Carboxylated ethylene-methyl copolymers (viii) Carboxylated ethylene-butyl acrylate copolymer (ix) Ethylene terpolymer (x) Maleic anhydride graft polymer.

[0027] The polymer may comprise 30-90 wt% of the formulation, preferably 50-80 wt%, and mixtures of these polymers may be used.

[0028] Preferred polymer blends containing tackifying resins are used, and preferred polymer systems include: (i) one or more ethylene / unsaturated ester copolymers, and (ii) Tackifying resin.

[0029] The choice of ethylene / unsaturated ester copolymer will depend on the intended use of the adhesive. However, particularly preferred mixtures include two ethylene-acrylate copolymers, as well as an ethylene-vinyl acetate copolymer and a tackifying resin. We have found that using a combination of high melt index ethylene-acrylate copolymers, ethylene-vinyl acetate copolymers, and tackifying resins provides low melt viscosity and good adhesion to oily surfaces at the application temperature.

[0030] In particular, we found that a combination of an ethylene-acrylate copolymer with a melt flow index of 320 g / 10 min (ISO1133 190 °C, 2.16 kg) and an ethylene-vinyl acetate copolymer with a melt flow index of 800 g / 10 min can achieve viscous adhesion failure.

[0031] The presence of a first crosslinking agent and a thixotropic filler further provides a dry adhesive that, upon application, can swell to produce an adhesive foam with good retention properties. The tackifying resin can be any resin known in the art, and can be an aliphatic or aromatic hydrocarbon resin, or a natural terpene-based resin. Preferred resins are those sold by CRAY VALLEY under the trade name Norsolene, particularly aromatic resins with softening points in the range of 95-115°C, such as Norsolene S105. The presence of an ethylene-vinyl acetate copolymer with the tackifying resin provides a formulation with a relatively low yield point and melt viscosity, which then allows oil to migrate from the metal surface into the polymer matrix, enabling the molten polymer to absorb surface contaminants. Furthermore, this allows the molten compound to adhere more readily to the surface. Based on the tackifying resin formulation, we preferably use 10-30 wt%.

[0032] The preferred polymer blend comprises a first ethylene / n-butyl acrylate copolymer containing 35 wt% n-butyl acrylate and having a melt flow index of 320 (g) / 10 min; a second ethylene / acrylate copolymer having a melt flow index of 8 g / 10 min; an ethylene / vinyl acetate copolymer containing 28 wt% vinyl acetate and having a melt flow index of 800 g / 10 min; and a hydrocarbon tackifying resin.

[0033] For example, we have found that the formulations of the present invention may have the following properties at the referenced shear rates.

[0034] When measuring strain at 1% on a parallel disk rheometer, preferably at 1s...-1 At shear rate and 90°C, the viscosity is in the range of 500-1000 Pa·s, while at 100 s⁻¹... -1 At the shear rate, the viscosity is in the range of 100-5000 Pa·s.

[0035] However, the benefits of lower viscosity must be balanced with the adhesive's ability to maintain its shape during the baking stage, trap gases during foaming, and prevent undesirable flow of the molten polymer system during the baking stage at the foaming temperature. Therefore, components that increase the polymer melt viscosity during foaming and baking cycles without impairing the flowability required for melt application of the adhesive (e.g., by extrusion) must be included. This is achieved by including a second crosslinking agent. Thixotropic fillers are preferably silica, with fumed silica being particularly useful. Other thixotropic fillers that can be used include polyamide waxes, acrylic polymers (especially high molecular weight polymers), layered silicates, and modified urea. We prefer to use treated silica to limit the absorption of unwanted components such as air, dust, and / or moisture during formulation storage, and organosilane-treated silica is preferred. We have found that fillers at 1 wt%–15 wt%, preferably 2 wt%–8 wt%, based on a total weight are particularly suitable for achieving the desired melt viscosity during curing and baking cycles.

[0036] Any suitable crosslinking agent with the desired activation temperature and crosslinking kinetics at an appropriate temperature can be used. Examples of suitable materials include sulfur-curing systems, peroxide-curing systems, resin-curing systems, and metal oxide-curing systems. Crosslinking systems include a first crosslinking agent with rapid kinetics at the low temperature at the start of baking (e.g., less than 30 minutes (half-life) at 100°C), and a second crosslinking agent with a longer (half-life) at the start of baking temperature (e.g., several hours) and a shorter (half-life) at the nominal baking temperature (e.g., less than 5 minutes at 150°C).

[0037] We found the combination of benzoyl peroxide (half-life of 23.4 min at 100 °C) and 1,1'-(di-tert-butylperoxide)-3,3,5-trimethylcyclohexane peroxide (half-life of 376 min at 100 °C and 1.3 min at 150 °C) to be particularly useful. During the baking stage of the adhesive, benzoyl peroxide will initially decompose below the foaming temperature, thereby forming a gel in the molten polymer formulation to increase its viscosity; we found that up to 0.1 wt%–5 wt% benzoyl peroxide is particularly useful based on the weight of the formulation. It can be used in the form of adsorption onto mineral fillers. 1,1'-(di-tert-butylperoxide)-3,3,5-trimethylcyclohexane peroxide decomposes slowly at the activation temperature and rapidly at the foaming temperature, thereby solidifying the foam structure and allowing for reuse at up to 0.1 wt%–5 wt%. The crosslinking system may also contain an activator for the crosslinking agent, which can be used to synchronize the crosslinking rate with the decomposition kinetics of the foaming agent. An example of an activator that can be used is bisphenol A diacrylate. The blowing agent is selected based on the temperature at which foaming is to be completed. The blowing agent can be a physical or chemical blowing agent. Physical blowing agents may include volatile gases collected in the thermoplastic shell, which soften and cause the gases to expand at the foaming temperature. However, chemical blowing agents that decompose to produce gases upon heating are preferred, such as azodicarbonamide, p-toluenesulfonyl hydrazide (TSH), and acetone oxidase (pp'oxybis)(benzene)sulfonyl hydrazine (OBSH), and are preferably used at 1-10 wt% based on the weight of the formulation. The foaming system may also include an activator that allows the expansion rate to be synchronized with the crosslinking reaction. Zinc oxide is a suitable activator, and can be used at 1-10 wt% based on the weight of the formulation.

[0038] Therefore, by appropriately selecting the crosslinking system and foaming agent system, the viscosity of the formulation from application to baking, expansion, and curing can be controlled to obtain sufficient adhesion, non-adhesive material at ambient temperature, material that maintains its shape during the baking stage, controlled foaming, and foam that maintains its structure. When the formulation of the present invention is applied to a substrate at a temperature of 70-120°C, excellent adhesion can generally be achieved, and foaming and the development of foaming and adhesion properties can be activated at temperatures of 140°C-220°C. During application, it is preferred that the melt viscosity index is 20-80 g 110(10) min at a load of 10 kg and 90°C.

[0039] Other materials that can be added are fillers, such as calcium carbonate and pigments.

[0040] In a preferred application of the adhesive formulation of the present invention in automobile manufacturing, the components are mixed and fed into an extruder, which heats the mixture to its softening point (between 70°C and 120°C) and forms it into continuous beads.

[0041] The molten beads can then be applied to the body panels, which are typically preheated before the adhesive is applied, as this improves the beads' tackiness. The preheating temperature should be similar to the melt temperature of the adhesive. The beads can be used using the extrusion technique described in U.S. Patent Publication 2006 / 0127584. After cooling, the components are assembled into the vehicle. The body panels undergo a corrosion-resistant treatment, sometimes called electrophoretic coating. During the electrophoretic coating baking process, the beads expand, adhere, and provide a seal between the component and its environment. This can be used for vibration damping, sound insulation, or sealing against dust and water for sealing purposes.

Claims

1. A system for sealing a cavity in a vehicle frame, comprising: (a) A wall that defines a cavity in the vehicle frame; (b) A thermoplastic expandable material, which contacts the wall before expanding, the thermoplastic expandable material comprising... (i) one or more solid polymers, (ii) Thixotropic fillers. (iii) Foaming agent system, and (iv) A crosslinking system comprising: a first crosslinking agent activated at a temperature within the range of the thermoplastic expandable material being heated to a foaming temperature to increase the melt viscosity of the thermoplastic expandable material during the baking stage; and a second crosslinking agent activated at a temperature within the foaming temperature range to crosslink the foamed thermoplastic expandable material. (c) An extruder for distributing the thermoplastic expandable material as beads on at least a portion of the wall, the thermoplastic expandable material being supplied to the extruder in granular form; and (d) A robot, wherein the extruder is connected to the robot, wherein the robot moves the extruder relative to the wall, the robot comprising: a camera that takes photographs of the thermoplastic expandable material beads, and a computer system that analyzes whether the thermoplastic expandable material is in the correct position and has the correct shape; The thermoplastic expandable material is dry at ambient temperature before and after it is disposed on the wall; The adhesive strength between the wall and the thermoplastic expandable material is 0.25-1.5 N / mm. 2 ;as well as When exposed to heat supplied to the vehicle frame during motor vehicle production, the thermoplastic expandable material expands by at least 800% during foaming compared to its unfoamed state.

2. The system of claim 1, wherein the thermoplastic expandable material is a thermally activated thermoplastic expandable material.

3. The system of claim 2, wherein the thermoplastic expandable material is an acoustic polymer.

4. The system of claim 1, wherein the wall is the inner wall of a hollow structural member.

5. The system of claim 1, wherein the wall is a vehicle body panel or a reinforcing member.

6. The system of claim 3, wherein when measured at 1% strain on a parallel disc rheometer, during the arrangement by the extruder, the thermoplastic expandable material in 1 second -1 At shear rate and 90°C, the viscosity is in the range of 500 to 1000 Pa·s, and within 100 s... -1 At the shear rate, the viscosity is in the range of 100 to 5000 Pa·s.

7. The system of claim 6, wherein the first crosslinking agent has an activation temperature of about 100°C to about 130°C; and wherein the second crosslinking agent has an activation temperature of about 140°C to about 180°C.

8. The system of claim 7, wherein the first crosslinking agent comprises benzoyl peroxide, which is present in an amount of 0.5% by weight; and wherein the second crosslinking agent comprises 1,1'-(di-tert-butylperoxide)-3,3,5-trimethylcyclohexaneperoxide, which is present in an amount of 1.5% by weight.

9. The system of claim 8, wherein the one or more solid polymers comprise two ethylene-acrylate copolymers and an ethylene-vinyl acetate copolymer and a tackifying resin.

10. The system of claim 9, wherein the one or more solid polymers comprise a combination of an ethylene-acrylate copolymer having a melt flow index of 320 g / 10 min and an ethylene-vinyl acetate copolymer having a melt flow index of 800 g / 10 min, wherein the melt flow index is 2.16 kg at 190 °C according to ISO 1133.