Praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
If the situation is as described in your question, then the money that you took from the sales manager of the nylon company is unlawful because you are an agent for the company where you work. Moreover, it is the duty of an agent to act to the best interest of the principal, not make money for himself. What you have done is an act of lying and eating up people`s wealth unjustly. Allah the Almighty Says {What means}: "And eat not up your property among yourselves in vanity, nor seek by it to gain the hearing of the judges that ye may knowingly devour a portion of the property of others wrongfully." {Al-Baqarah, 188}. You are required to return the amount that you took in addition to seeking repentance and asking Allah to forgive you for what you have done. And Allah the Almighty Knows Best.