Vibration damping material, structural laminates, and processes for making same

Abstract

Viscoelastic resin compositions are provided, comprising aliphatic polyamide, polyamide 6T6I, and select plasticizers, all in advantageous weight percentages. Structural laminates including such compositions are also disclosed.

Description

DETAILED DESCRIPTION OF THE INVENTION

The composition of the present invention contains containing (1) 20-95 wt % of aliphatic polylamide, (2) 1-40 wt % of amorphous polyamide, (3) 0.5-20 wt % of a plasticizer, where the total composition represents 100 wt %.

The polyamide resin composition of the present invention can realize a high dynamic viscoelasticity (tan δ) over a wide temperature range and can provide molding products with excellent dampening property. It is known that the maximum dampening performance will be displayed around the tan δ peak temperature (see for example, Rao, M. D., “Recent Applications of Viscoelastic Damping for Noise Control in Automobiles and Commercial Airplanes”, Journal of Sound and Vibration, Vol 262, (3), 2003, pp 457-474; also Ross, D., Ungar, E. E. and Kerwin, E. M., in Structural Dampening, J. E. Ruzicka ed., ASME, New York, 1959, Sec 3; and Kerwin, E. M., Ungar, J. R., and Rice, E., Sound and vibration damping with polymers; Proceedings of the Symposium, 197^th National Meeting of the American Chemical Society, Dallas, Tex., 1989, Proceedings 1990, pp 317-345). The composition of the present invention demonstrates an increased tan δ used as the scale for dampening property. In particular, the composition of the present invention has a relatively low tan δ peak temperature (about 30-100° C.) and can increase tan δ to a high level than in conventional technology. The composition of the present invention can provide molding products with high dampening capability in an average and even in a relatively low temperature range (for example, 50-80° C.) for example for automobile engine compartments. Also, the composition of the present can maintain or improve rigidity and other mechanical characteristics.

Consequently, the polyamide resin composition of the present invention has a tan δ peak temperature in the range of 30-100° C., preferably, in the range of 50-90° C.

In the following, each component in the composition of the present invention will be described.

Aliphatic Polyamide

There is no particular limitation on the aliphatic polyamide, which can be polyamide 46, polyamide 66, polyamide 610, polyamide 612, polyamide 6, polyamide 11, polyamide 1010, polyamide 1012, polyamide 12, copolymer of PA66 and polyamide 6, copolymer of PA66 and polyamide 610, copolymer of PA66 and polyamide 612, etc. These polyamides can be used either alone or as a mixture of several types. It is preferred to use PA6 in the present invention.

Amorphous Polyamide

For the amorphous polyamide of the invention the crystal melting heat quantity measured by a differential scanning calorimeter (DSC) is less than 1 cal/g. An example of amorphous polyamide has repeated units comprised of a part derived from an aromatic carboxylic acid and a part derived from aliphatic diamine.

Although there is no special limitation on the aforementioned aromatic carboxylic acid, terephthalic acid and its derivatives and isophthalic acid and its derivatives are preferred. In addition to the aforementioned aromatic carboxylic acid, it is also possible to use succinic acid, adipic acid, suberic acid, sebacic acid, dodecanoic diacid, or other aliphatic carboxylic acids as long as the purpose of the invention is not adversely affected.

Examples of the aforementioned aliphatic diamine include hexamethylene diamine, tetramethylene diamine, 2,5-dimethylhexamethylene diamine, etc.

In the present invention, as described above, an aromatic polyamide derived from aliphatic diamine terephthalic acid and its derivatives or isophthalic acid and its derivatives or other monomers can be used. An example is 6T/6I. In this case, “T” represents a polymer derived from terephthalic acid and its derivative, while “I” represents a polymer derived from isophthalic acid and its derivatives.

The aforementioned amorphous polyamide, for example, can be manufactured as follows. That is, the amorphous polyamide can be manufactured by a polycondensation reaction from the salt of the aforementioned aromatic carboxylic acid and aliphatic diamine. Polymerization is carried out using the conventional melt polymerization method, solid-state polymerization method, solution polymerization method, interfacial polymerization method, etc.

Although the aforementioned amorphous polyamide can be manufactured as described above, it is also possible to use commercially available products, such as Amodel A-1000 (product of Amoco Polymer Corporation) and Zytel® HTN (product of E.I. DuPont de Nemours & Co., Wilmington, Del.).

The content of the aliphatic polyamide component (1) in the polyamide resin composition of the present invention is in the range of 20-95 wt %, preferably, in the range of 30-90 wt % based on the weight of the composition. The content of amorphous polyamide component (2) is in the range of 1-40 wt %, preferably, in the range of 2-20 wt % based on the weight of the composition.

Plasticizer

There is no particular limitation on the plasticizer used in the present invention as long as it is compatible with aliphatic polyamide component (1) and/or amorphous polyamide component (2). Examples include without limitation water, alcohol, caprolactam, oligomeric amides, sulfone amide type compounds, benzoate type compound, and metal halides. The plasticizer can be pre blended or compounded into one or both of the aforementioned polyamide (such as aliphatic polyamide) or it can be added into the composition of the present invention in other ways. In the present invention, the tan δ peak temperature of the mixture becomes higher than that of the aliphatic polyamide when the amorphous polyamide is mixed with the aliphatic polyamide. However, it returns to the low value when the plasticizer is added. In the present invention, when the plasticizer is added as described above, the tan δ peak temperature of the entire composition (mixture) can be lowered, and the dynamic viscoelasticity (tan δ) of the molding product formed from the composition of the present invention can be increased. The rigidity and other mechanical characteristics of the molding product formed using the composition of the present invention can also be improved.

In the present invention, the content of the plasticizer is in the range of 0.5-20 wt % based on the total formulation.

Inorganic Filler

The polyamide resin composition of the present invention may also contain filler. Examples of filler include glass fiber, carbon fiber, mica, talc, kaolin, wollastonite, calcium carbonate, and potassium titanate. These fillers can be used either alone or as a mixture of several types. In a preferred embodiment, glass fiber is used since it can improve the rigidity of the resin composition. Also, mica or talc are also preferred fillers.

In the present invention, the content of the inorganic filler is in the range of 0-60 wt %.

If necessary, other additives besides the aforementioned inorganic filler can also be added into the polyamide resin composition of the present invention. Examples of the aforementioned additives include thermal stabilizers, UV absorbents, antioxidants, lubricants, nuclear agents, antistatic agents, demolding agents, dye type coloring agents, pigment type coloring agents, flame retardants, plasticizers, and other resins.

The content of these additives are variable depending on the purpose of the additives. For example, it is preferred to be in the range of 0-10 wt % based on the total weight of the composition.

The composition of the present invention is the form of a mixture homogeneously dispersed in a polymer matrix such that all of the nonpolymerized components are integrated in the entire mixture. The mixture can be obtained by mixing the various components using any melt mixing method. Examples of the melt mixing method include the method in which the various components are homogeneously mixed using a monoaxial or biaxial screw extruder, blender, kneader, Banbury mixer, or other melt mixer (method that melts and mixes the various components of the composition of the present invention at the same time), or the method, in which some of the aforementioned materials are added sequentially or in a special combination by a melt mixer, followed by adding the rest of the materials and performing melt mixing until a homogenous mixture is obtained (the method using multiple stages). In the present invention, it is preferred to perform mixing in a special procedure as in the molding product manufacturing method to be described later. The mixing operation can be carried out continuously or using the batch method. Also, when the composition is prepared in multiple stages, it is also possible to temporarily cool, off and solidify the mixed components between the stages.

The present invention is also directed to a method for manufacturing a molding product using the aforementioned polyamide resin composition.

The first embodiment of the manufacturing method disclosed in the present invention includes (a) a step of mixing and melt blending (1) aliphatic polyamide, (2) amorphous polyamide, and (3) plasticizer and (b) a step of molding the molding product using the composition obtained in step (1).

In the manufacturing method of the present invention, first, the composition of the present invention is mixed by following any of the procedures explained above for the composition manufacturing method. Then, the obtained composition is molded using an injection molding method, blow molding method, sheet molding method, vacuum molding method, or other molding method. The molding conditions can be selected appropriately corresponding to each means. The conventional conditions can be used.

The polyamide resin composition of the present invention has a relatively low tan δ peak temperature (for example, about 30-100° C.). The molding product obtained using the manufacturing method of the present invention has higher tan δ than that in the conventional technology.

The second embodiment of the manufacturing method disclosed in the present invention includes (A) a step, in which (2) amorphous polyamide is added into (1) aliphatic polyamide to obtain a mixture having a tan δ peak temperature higher than that of the aliphatic polyamide, (B) a step, in which (3) plasticizer is added into the mixture obtained in step (A) to obtain a mixture having a tan δ peak temperature lower than the tan δ peak temperature of the mixture obtained in step (A), (C) a step, in which the mixture obtained in step (B) is used to form a molding product having a high dynamic viscoelasticity (tan δ).

In the second embodiment of the manufacturing method, in step (A), the tan δ peak temperature of the mixture can be increased higher than that of the aliphatic polyamide by adding the amorphous polyamide into the aliphatic polyamide. The increased tan δ peak temperature can be returned to the low value again by adding the plasticizer in step (B). When the plasticizer is added, the dynamic visoelasticity (tan δ) of the molding product obtained from the composition (mixture) can also be increased. The rigidity and other mechanical characteristics of the molding product obtained from the composition (mixture) of the present invention can also be improved.

The dynamic visoelasticity (tan δ) is expressed by the following equation.

tan δ=E″/E′

where, E″ represents the loss visoelasticity, E′ represents storage viscoelasticity.

In the second embodiment of the manufacturing method of the present invention, first, amorphous polyamide (2) is mixed with aliphatic polyamide (1). Then, the plasticizer is added into the obtained mixture and mixed. The composition of the present invention is obtained in this way. The obtained composition is molded using the injection molding method, blow molding method, sheet molding method, vacuum molding method, or other molding method to obtain the molding product. The molding conditions can be selected appropriately corresponding to each means. The conventional conditions can be used.

The molding product obtained using the method of the present invention can be used for various types of structural materials, various types of housing materials, automobile parts, household electrical products, electronic machine parts, construction materials, etc.

EXAMPLES

In the following, the present invention will be explained in more detail with reference to application examples and comparative examples. The present invention, however, is not limited to the examples.

Preparation of the Composition

Various components were mixed by a biaxial kneader in the composition shown in Table 1. The obtained mixture was pelletized. The various components were mixed at the same time, although they equally well could be mixed in the order of aliphatic polyamide, amorphous polyamide, and plasticizer.

Production of Test Sample

The pellets obtained as described above were subjected to injection molding performed using an injection molding machine to obtain a test sample.

Measurement of Tan δ

The test sample (sample size: 55×10×4 mm) obtained as described above was measured under the conditions of measurement temperature: 0-150° C. and frequency: 2 Hz using 983 Dynamic Mechanical Analyzer produced by DuPont Instruments Corporation.

Measurement of Flex [Flexural] Modulus

The test sample obtained using the aforementioned method was measured according to ISO 178.

The following materials were used as the components for the composition of the application examples and comparative examples.

Aliphatic polyamide: Zytel® FE7330J produced by Dupont, Zytel® 21A NC010 (containing 7% of caprolactam (plasticizer)) produced by Dupont

Amorphous polyamide (aromatic amorphous polyamide): Zytel® HTN503 produced by Dupont

Plasticizer: Caprolactam (contained in an amount of 7% in aliphatic polyamide (Zytel 21A NC010; produced by Dupont))

Inorganic filler: Glass fiber (CS FT756D; product of Asahi Glass Co., Ltd.)

TABLE 1
	Comparative	Comparative	Comparative	Application
	Example 1	Example 2	Example 3	Example 1
Composition	(wt %)	(wt %)	(wt %)	(wt %)
Aliphatic	70.0	56.2		—
polyamide
(Zytel FE7330)
Plasticizer-	—	—	70.0	56.2
containing
aliphatic
polyamide
(Zytel
21A NC010a)
Amorphous	—	13.8		13.8
polyamide
(Zytel
HTN503)
Inorganic filler	30.0	30.0	30.0	30.0
(CS FT756D)

Results

The characteristics of the composition of the present invention are shown in Table 2.

	TABLE 2
		Com-	Com-	Com-	Appli-
		parative	parative	parative	cation
		Example 1	Example 2	Example 3	Example 1
Flex [Flexural]	MPa	8670	8790	7850	9090
Modulus
Tanδ peak		0.069	0.125	0.077	0.141
value
Tanδ peak	° C.	79	91	63	83
temperature
Tanδ at 50° C.		0.026	0.019	0.064	0.030
(1)
Tanδ at 60° C.		0.041	0.035	0.076	0.057
(2)
Tanδ at 70° C.		0.062	0.061	0.074	0.106
(3)
Tanδ at 80° C.		0.069	0.100	0.063	0.140
(4)
(1) + (2) + (3) +		0.198	0.215	0.277	0.333
(4)

As can be seen from the results shown in Table 2, the polyamide resin composition of the present invention not only has a higher tan δ peak than the conventional example but also has higher tan δ in average in a wide temperature range of 50-80° C., which means it has an excellent dampening property.

The polyamide resin composition of the present invention also has excellent rigidity compared with Comparative Examples 1, 2, 3.

Claims

1. A composition comprising (i) between 20-95 wt % of an aliphatic polyamide,(ii) between 1-40 wt % of a polyamide PA6T6I, and(iii) between 0.5-20 wt % of a plasticizer, where the weight percentages are by weight of total formulation, and in which the aliphatic polyamide is miscible with the polyamide PA6T6I and the plasticizer is selected from the group consisting of caprolactam, oligoamide, sulfone amide and benzoate.

2. A metal-polymer-metal structural laminate comprising a core of polymeric material having adhered to each side thereof a metal skin layer wherein: (a) said metal skin layer is about 0.1 mm to about 10 mm thick;(b) said laminate has a ratio of core thickness to skin thickness of between about 1:3 and about 20:1;(c) said laminate total thickness is between about 0.3 mm and about 10 mm;(d) said polymeric material comprises(i) between 20-95 wt % of an aliphatic polyamide,(ii) between 1-40 wt % of a polyamide PA6T6I,(iii) between 0.5-20 wt % of a plasticizer, where the weight percentages are by weight of total formulation, and in which the aliphatic polyamide is miscible with the polyamide PA6T6I and the plasticizer is selected from the group consisting of caprolactam, oligoamide, sulfone amide and benzoate.

3. The structural laminate of claim 2 wherein the metal skin layers on each side of the core are different thicknesses.

4. The structural laminate of claim 2 wherein the metal skin layers on each side of the core comprise different metals.

5. The laminate of claim 2 wherein the ratio of core thickness to skin thickness is between 1:2 and 3:1.

6. The laminate of claim 2 wherein the total laminate thickness is between 0.6 mm and 1.5 mm.

7. The laminate of claim 2 wherein the core comprises a solid filler.

8. The structural laminate of claim 2 wherein the metal skin is steel.

9. The structural laminate of claim 2 wherein the metal skin is aluminum.

10. A method for manufacturing a [sound] dampening molding product characterized by having (a) a step of mixing (1) aliphatic polyamide, (2) amorphous polyamide, and (3) plasticizer,(b) a step of molding the molding product using the composition obtained in step (a).

11. A method for manufacturing said dampening molding product characterized by having (A) a step, in which (2) amorphous polyamide is added into (1) aliphatic polyamide to obtain a mixture having a tan δ peak temperature higher than that of the aliphatic polyamide,(B) a step, in which (3) plasticizer is added into the mixture obtained in step (A) to obtain a mixture having a tan δ peak temperature lower than the tan δ peak temperature of the mixture obtained in step (A),(C) a step, in which the mixture obtained in step (B) is used to form a molding product having a high dynamic viscoelasticity (tan δ).