KR101127262B1 - Preliminary moisture-absorbing method and apparatus for polyamides resin article - Google Patents

Abstract

Provided are a method and an apparatus for pre-moisturizing a polyamide resin molded article using water. The method may include removing or minimizing calcium carbonate from the water to be used for the pre-moisture absorption and contacting the polyamide resin molded article with water from which the calcium carbonate has been removed or minimized to pre-moisture the polyamide resin molded article. have.

Polyamide resin, moisture absorption, calcium carbonate, whitening phenomenon, dimensional stability, vibration, noise

Description

Preliminary moisture-absorbing method and apparatus for polyamides resin article}

The present specification relates to a method and apparatus for pre-moisture absorption of polyamide (Polyamids, PA) resin molded articles such as nylon. More specifically, the present invention relates to a moisture absorption method and apparatus for a polyamide resin molded article which can prevent whitening phenomenon occurring during prior moisture absorption of the polyamide resin molded article.

Polyamide resins have very high hygroscopicity compared to other resins. Therefore, when the polyamide resin is left in the air, the dimensions tend to change by absorbing water vapor in the air. This results in a problem that molded articles made of polyamide resin have poor dimensional stability. For example, a polyamide resin molded article that had a moisture absorption rate (percentage of water absorbed relative to the total weight of the material) at an initial 0% absorbs water vapor in the air when exposed to the outside over a long period of time (for example, about 1 year). The dimensional change occurs. This dimensional change causes warpage due to product cracking or deformation, which in turn causes vibration, noise and other degradation of properties.

In order to prevent deterioration of the quality of the polyimide resin molded article due to moisture absorption and vibration or noise problems, it was stored in a dry place after molding before use, or stored in a container equipped with a moisture proof facility, or used after drying in a vacuum dryer. These methods minimize the amount of moisture contained by avoiding contact with moisture in the air or by drying as much as possible.

However, in the above methods, even if the dimensional safety can be temporarily secured, there is a problem that moisture absorption occurs again after a certain period of use.

In the present invention, not only the dimensional instability due to the high moisture absorption properties of the polyimide resin, and the problems such as vibration and noise generation, lowering of physical properties, etc. can be eliminated through the pre-moisture absorption process of the molded article of polyimide resin, The present invention provides a method and apparatus for pre-moisture absorption of a polyamide resin molded article capable of suppressing or preventing occurrence of whitening that may occur in a polyimide resin molded article.

In an embodiment of the present invention, there is provided a method for pre-hygroscopicity of a polyamide resin molded article in which the polyamide resin molded article is pre-moistured with water. In the above method, water in the liquid state or the vapor state can be used to pre-hygroscopic. The method also includes removing or minimizing calcium carbonate from the water to be used for the pre-moisture absorption and contacting the polyamide resin molded product in a liquid or vapor state with the calcium carbonate removed or minimized to form the polyamide resin molded article. It may include the step of pre-hygroscopic.

In another embodiment of the present invention, there is provided a pre-moisture absorption device for a polyamide resin molded article including a pre-moisture absorption portion for pre-humidifying the polyamide resin molded article with water. The apparatus may include a calcium carbonate removal unit for removing or minimizing calcium carbonate from the water to be used for the pre-moisture absorption, and a pre-hygroscopic unit for contacting the polyamide resin molded article with water in which the calcium carbonate is removed or minimized.

The pre-moistured polyamide resin molded article obtained according to the embodiments of the present invention is not only a problem of moisture absorption and consequent dimensional instability, vibration and noise generation, deterioration of physical properties, but also used as an exterior part because of its good appearance without whitening. Suitable. In particular, according to the pre-moisture absorption according to the embodiments of the present invention, the physical properties (for example, impact strength) are rather improved in comparison with the case where there is no pre-moisture absorption, and such physical property improvement can be achieved even in a short time (for example, about 5 hours or less). .

Hereinafter, exemplary embodiments of the present invention will be described.

In the present specification, the pre-moisture absorption means that the polyamide resin molded article is prevented from being absorbed in the air by being absorbed in advance before being placed in the absorbed state in the air.

In this specification, the hot water means water having a temperature of more than 50 ° C. and less than 100 ° C.

In the present specification, hot water means water at room temperature (25 ° C.) to 50 ° C.

After the polyamide resin is absorbed to some extent, it may reach a state where it is no longer absorbed. In this state, since it no longer absorbs moisture, it may exhibit dimensional stability. In this dimensional stable state, the physical properties inherent to the polyamide resin, such as impact resistance, may be exhibited, and vibrations or noises may be equally or rather reduced. This state may be referred to as a moisture absorption equilibrium state. For reference, when a material is in an equilibrium absorption state, the absorption rate, that is, the equilibrium absorption rate varies slightly depending on temperature and humidity, but is generally about 2.4% for nylon 6 and about 1.5% for nylon 66.

In exemplary embodiments of the present invention, the above-described pre-hygroscopicity is first performed using water. In this pre-moisture absorption method, the polyamide resin molded article is absorbed to reach a moisture absorption equilibrium state, thereby inducing dimensional stability, thereby preventing vibration, noise generation problems, or other deterioration of physical properties.

Non-limiting examples of the pre-moisture absorption method include a method of pre-moisturizing a polyamide resin-formed product using water vapor (steam absorption method), a method of pre-moisture-forming a polyamide resin molded article with hot water (hydrothermal moisture absorption method), lukewarm hot water And a method of pre-humidifying the polyamide resin molded article (hot water absorption method).

On the other hand, embodiments of the present invention also pay attention to the whitening phenomenon occurs after the absorption in the pre-hygroscopic process itself as described above to solve this.

That is, according to the results of the inventors of the present invention, calcium carbonate (CaCO ₃ ) contained in moisture during pre-moisture absorption may be fixed to the polyamide component, and whitening may occur. For reference, calcium carbonate has strong corrosion and surface adsorption properties that are known to melt rocks after prolonged exposure, as is well known.

For example, when pre-moistured in boiling water, calcium carbonate (CaCO ₃ ) contained in the water may be fixed to the polyamide, thereby causing surface whitening, thereby resulting in appearance defects. Polyamide resin molded articles in which appearance defects occur are difficult to use as products.

Therefore, in the embodiments of the present invention, the carbonic acid is removed from the water used for the moisture absorption when the pre-humidification process is performed, and then the whitening phenomenon of the final resin molded product is suppressed or prevented by performing the pre-moisture absorption with the water from which the carbonic acid has been removed.

In addition, embodiments of the present invention provides a pre-moisture absorption device of a polyamide resin molded article including a pre-moisture absorption unit for pre-moisture-proof the polyamide resin molded article using water. The apparatus may include a calcium carbonate removal unit for removing or minimizing calcium carbonate from the water to be used for the pre-moisture absorption, and a pre-hygroscopic unit for contacting the polyamide resin molded article with water in which the calcium carbonate is removed or minimized.

1 is a schematic diagram illustrating a hygroscopic process according to one non-limiting embodiment of the present invention.

Referring to FIG. 1, the moisture absorption process may consist of, for example, the following process. That is, in one non-limiting embodiment of the present invention, first, the water to be used in the pre-hygroscopic process is passed through the activated carbon filter as a first process (a of FIG. 1). That is, in order to remove calcium carbonate showing a whitening phenomenon, water used for moisture absorption is passed through an active carbon filter. Accordingly, the whitening phenomenon can be prevented by preliminarily removing the calcium carbonate contained in the water and then absorbing the polyimide molded product with the water from which the calcium carbonate is removed. Calcium carbonate causing whitening is removed by adhering to the surface of activated carbon while passing through activated carbon filter.

Activated carbon used in the activated carbon filter is black porous carbon obtained by activating wood, sawdust, palm bark, coal and the like, and may adsorb or remove organic substances in water. Such activated carbon is preferably ph 4-11, more than arsenic 0ppm and more than 2ppm, lead more than 0ppm and 10ppm or less, iodine adsorption force of 950 mg / g or more (for example, 950 to 9500 mg / g). If the iodine adsorption capacity is out of conditions, calcium carbonate may not be properly removed in water, and whitening may occur in some or all nylon products introduced into the moisture absorption process.

2 is a schematic diagram showing an activated carbon filter which is a calcium carbonate remover according to a non-limiting embodiment of the present invention. 2 schematically illustrates one activated carbon filter, but it will be understood by those skilled in the art that a plurality of activated carbon filters may be used in a manner such as stacking the activated carbon filters.

Referring to FIG. 2, the activated carbon filter includes an activated carbon 10, an activated carbon storage space 20 capable of storing the activated carbon 10, and a net installed in the storage space 20 and used for pre-absorption. The same water passage member 21 is included. Here, the storage space is made of metal, preferably Sus material. In the case of the manufacture of the sus since it is possible to prevent the rust of the filter due to moisture in advance is preferable.

Calcium carbonate in the water may be removed while the water passing through the water passage member 21 passes through the activated carbon 10 stored in the storage space 20. The activated carbon 10 to be filled in the activated carbon filter is washed with clean water before being filled in the filter to wash the fine activated carbon particles on the surface of the activated carbon. If the fine activated carbon particles are not removed, the fine particles remain in the water and adhere to the surface of the polyamide resin molded article while undergoing a pre-moisture absorption. The activated carbon washed in water is transferred to an activated carbon filter and passed through the water so that calcium carbonate in the water is removed by the activated carbon. This process is an important process for preventing the surface whitening that occurs after the pre-moisture absorption process.

Referring back to FIG. 1, the polyamide resin molded article is pre-absorbed using water passed through the activated carbon filter (b in FIG. 1). This pre-humidification process can proceed as follows, for example.

That is, the polyamide resin molded article to be pre-moistured is loaded into the chamber, and the water is vaporized and provided in the chamber to bring vapor into contact with the polyamide resin molded article (steam absorption method), or the water is, for example, 70-85. It is heated to a temperature of about ℃ to make hot water and then provided in the chamber so that the polyamide resin molded article is in contact with the hot water (immersion in hot water) (hydrothermal absorption method), or the water is lukewarm hot water, for example about 40 ~ 45 ℃ There is a method (hot water absorption method) in which a polyamide resin molded article is in contact with hot water (submerged in warm water) by making it into the chamber after making it. Among the above methods, the hydrothermal moisture absorption method is particularly preferable in that the time for reaching the target moisture absorption rate is very fast, that is, the moisture absorption rate per unit time is very high.

After supplying the water for pre-absorption which passed the activated carbon filter to the said pre-moisture absorption chamber, the polyamide resin molded object for pre-moisture absorption may be loaded in the chamber. In this process, the polyamide resin molded part and the metal parts of the machine are assembled so that the parts assembled with each other face downward so that water does not accumulate in the assembly part and prevents appearance stains.

Hereinafter, the vapor absorption, hot water absorption, and hot water absorption will be described in detail.

In a non-limiting example, in the vapor absorption process, the atmosphere in the chamber is raised to, for example, the specified temperature of 85 ° C., and then, for example, steam is introduced after a predetermined time in a state of maintaining the atmosphere for 30 minutes, so that the relative humidity is not less than 90% and less than 100%. Moisture can be started while maintaining, and the atmosphere can be maintained until the target moisture absorption rate is reached.

In a non-limiting example, in a hydrothermal or hot water absorption process, the water injected into the loaded chamber is filled and the polyamide resin molded article is completely immersed in the water. At this time, the water is heated to each prescribed temperature, and maintained at a prescribed temperature (for example, 80 to 85 ° C. for hot water and 40 to 45 ° C. for hot water) for at least 1 hour until the target moisture absorption rate is reached. The material of the chamber immersed in water is preferably made of sus material to prevent rust. When the moisture absorption process is completed, in the vapor absorption method, when the target moisture absorption rate is reached, the temperature inside the moisture absorption chamber is lowered to 20 ° C., and the product is taken out. For your reference, special attention should be paid to the injury of workers during the hydrothermal absorption process. In the hydrothermal absorption method, when the target moisture absorption rate is reached, the user wears safety equipment (gloves, etc.) and takes out the product from the chamber. Remove any water remaining in the product with an air gun or blower and dry it in a separate place. The target moisture absorption rate is the equilibrium moisture absorption rate, which is the same in vapor absorption, hot water absorption, and hot water absorption, respectively, and should be within 1.5 to 2.4% (percent of weight after absorption to weight before absorption). The target moisture absorption rate of 1.5 to 2.4% is to be the same as the equilibrium moisture absorption rate when the polyamide molded article is placed in the air without prior moisture absorption. In the present invention, the target moisture absorption in a short time through the prior moisture absorption. Rate can be achieved. For reference, when the target moisture absorption rate is more than 2.4%, the absorbed water may be discharged from the molded article again.

The vapor in the chamber is then evacuated and the product is evacuated and then visually inspected (C in FIG. 1). In the visual inspection, after determining the appearance defects such as the whitening phenomenon of the polyamide resin molded article and the life of activated carbon, the pre-humidification step is completed.

Hereinafter, one non-limiting example embodiment will be described in more detail with respect to one of the exemplary embodiments of the present invention in comparison with the comparative example.

Example 1: Hydrothermal Hygroscopic Method

Power tool housings made of nylon (such as nylon 6) were pre-hygroscopic. The water was passed through an activated carbon filter containing activated carbon and the power tool housing was immersed in the water passed through the activated carbon filter. Hot water absorption was performed for 2 to 4 hours at 80 ~ 85 ℃.

As a result of hydrothermal absorption, it took 3.2 hours to reach the target moisture absorption rate (1.5-2.4%) under the hydrothermal conditions. In this way, the hydrothermal moisture absorption method was able to confirm the advantage of a very high moisture absorption per unit time. In addition, the appearance of the power tool housing after hydrothermal moisture absorption obtained good results without whitening.

Example 2: Hot water absorption method

In the same manner as in Example 1, a hot water absorption method was used instead of the hot water absorption. That is, in order to reach a target moisture absorption rate (1.5-2.4%) with hot water of 45 degreeC of water, it immersed about 100 hours. Since it takes a long time to absorb moisture, it is difficult to apply mass production due to productivity problems, but the whitening phenomenon did not occur and the appearance was good.

Example 3: Steam Hygroscopic Method

In the same manner as in Example 1, a steam adsorption method was used instead of hydrothermal adsorption. The target moisture absorption rate at the time of water vapor absorption was also 1.5 to 2.4%. The molded article was loaded into a chamber and steam was provided to the chamber. In the chamber, after raising the temperature of the chamber to a temperature of 70 ~ 85 ℃, the relative humidity was maintained at more than 90% and less than 100%. As a result of steam moisture absorption, the moisture absorption time was 5 hours or less, and the appearance of the moisture absorption part was also good. This steam absorption method confirmed that the change of moisture absorption rate with time was almost linearly proportional. The following table shows the change in moisture absorption rate with time.

Time (Hr) Weight before absorption (g) Weight after moisture absorption (g) Hygroscopicity (%) One 180.66 183.66 1.66 2 180.69 184 1.83 3 180.65 184.09 1.90 4 180.67 184.5 2.12 5 180.68 185.01 2.39

Impact strength, vibration, noise, diameter dimension change, and bleaching occur for 6 pieces of power tool housings (gear cover (vibration generating part) and handle part (part which transmits vibration to human body)) pre-moisture absorption. The degree of increase was measured and averaged as compared with the case without prior hygroscopic treatment and is shown in the following table.

Vibration measurements were measured using a contact vibration meter at the vibration measurement position. The vibration measurement unit was m / s ² .

The noise was measured 1m in front of the noise meter in the silent room, and the front, rear, left and right noises were measured. The unit of measure for noise was dB.

For the dimensional change, four partial sections were selected from the left side to the right side of the power tool, and the value after the moisture absorption was subtracted from the value before the moisture absorption with respect to the diameter of the section. For the measurement, the variation of the circumference was evaluated using a three-dimensional measuring instrument manufactured by Carl Zeitz.

Whether or not whitening occurred was visually determined.

Impact strength measured Izod impact strength. The unit of impact strength was kg? Cm / cm.

Impact strength vibration noise Diameter dimension change Whitening phenomenon Example 1
(Hydrogen Hygroscopic) 200% improvement 15-20% improvement 5% or less -0.02 ~ -0.15mm
(Shrink) Does not occur Example 2
(Hot water absorption) 200% improvement 15-20% improvement 5% or less -0.02-0.15mm
(Shrink) Does not occur Example 3
(Steam absorption) 200% improvement 15-20% improvement 5% or less -0.02 ~ -0.15mm
(Shrink) Does not occur

As described above, according to the embodiments of the present invention, the dimensional change is small, and the properties of vibration, noise, and impact strength are rather improved. For reference, when the weight is 1kg, the drop height is adjusted to 0.7-1.6m, and the hitting position is not broken when the hitting position is the weak line WELD LINE. In addition, all of the examples having a moisture absorption rate of 2.4% or less showed shrinkage. For reference, if the moisture absorption rate is 2.7% or more, it may be expanded.

In the case of the above embodiments, the whitening phenomenon did not occur even after the pre-humidification process.

Although the non-limiting and exemplary embodiments of the present invention have been described above, the technical idea of the present invention is not limited to the accompanying drawings and the above description. It will be apparent to those skilled in the art that various forms of modifications can be made without departing from the spirit of the present invention, and furthermore, such modifications will be within the scope of the claims of the present invention.

1 is a schematic diagram illustrating a hygroscopic process according to an exemplary embodiment of the present invention.

2 is a schematic diagram illustrating an activated carbon filter according to an exemplary embodiment of the present invention.

Claims (16)

delete As a pre-moisture absorption method of a polyamide resin molded article which pre-moistures a polyamide resin molded article using water, Removing or minimizing calcium carbonate from the water to be used to pre-moisture the polyamide resin molded article; And And pre-moisturizing the polyamide resin molded article by contacting the polyamide resin molded article in a liquid or vapor state with water from which the calcium carbonate has been removed or minimized. The method of claim 2, A method of pre-moisture absorption of a polyamide resin molded article which removes or minimizes calcium carbonate by passing water to be used for the pre-moisture absorption through activated carbon. The method of claim 3, wherein The said activated carbon is a moisture absorption method of the polyamide resin molded article whose iodine adsorption force is 950 mg / g or more. The method of claim 3, wherein A method for pre-hygroscopicity of a polyamide resin molded article which washes the activated carbon to prevent inflow of activated carbon particles into the water. The method according to any one of claims 2 to 5, Said pre-moisture absorption method is the vapor absorption using water vapor, the hot water absorption using hot water below 50 degreeC and less than 100 degreeC, or the hot water absorption using hot water of 25 degreeC-50 degreeC, The pre-moisture absorption method of the polyamide resin molded article. The method according to any one of claims 2 to 5, The said pre-moisture absorption method is a pre-moisture absorption method of the polyamide resin molded article which makes a pre-moisture absorption reach an equilibrium moisture absorption. The method of claim 7, wherein The equilibrium moisture absorption rate is 1.5 to 2.4% pre-moisture absorption method of the polyamide resin molded article. The method according to any one of claims 2 to 5, The pre-moisture absorption method is a vapor absorption method using water vapor, wherein the molded article is loaded into a chamber and water vapor is provided to the chamber. In the chamber, after raising the temperature of the chamber to a temperature of 70 to 85 ° C., a relative humidity of 90% The pre-moisture absorption method of the polyamide resin molded article which keeps more than 100% and a pre-moisture absorption reaches an equilibrium moisture absorption. The method according to any one of claims 2 to 5, The pre-moisture absorption method is a hydrothermal moisture absorption method, wherein the polyamide resin molded article is immersed in hot water at 80 to 85 ° C. for 1 to 4 hours so that the pre-moisture rate reaches the equilibrium moisture absorption rate. The method according to any one of claims 2 to 5, The pre-moisture absorption method is a hot water absorption method, the pre-moisture absorption method of a polyamide resin molded article soaking the polyamide resin molded article in hot water at 40 ~ 45 ℃ for 1 hour to 100 hours to reach the equilibrium moisture absorption rate. delete As a pre-moisture absorption device of a polyamide resin molded article which pre-moistures a polyamide resin molded article using water, The pre-moisture absorption device is a calcium carbonate removal unit for removing or minimizing calcium carbonate from the water to be used for the pre-moisture absorption; And And a pre-moisture portion for contacting the polyamide resin molded article in a liquid or water vapor state in which the calcium carbonate has been removed or minimized. The method of claim 13, The calcium carbonate removal unit is a pre-moisture absorption device of a polyamide resin molded article for passing the water to be used for pre-moisture absorption through activated carbon. The method of claim 13, The calcium carbonate removal unit is an activated carbon filter, The activated carbon filter is activated carbon; A storage space for storing the activated carbon; And a water permeable member through which the water can pass. The method according to any one of claims 13 to 15, The pre-humidification unit includes a chamber in which the molded article is loaded, wherein the water is supplied to the chamber as water vapor, hot water above 50 ° C. and below 100 ° C., or hot water at 25 ° C. to 50 ° C.

Images